When a formula contains several operators, there is a predetermined order in which they will be performed:

( ) Parentheses
^Exponents
* or / Multiplication or Division
+ or - Addition or Subtraction

(Forgetful? This phrase will help you remember: P lease E xcuse M y D ear A unt S ally).

In addition to the standard math operators, Excel has % which divides a value by 100. Like the minus sign used to negate values, % takes precedence over the standard operators.

Since Excel treats dates and times as numbers, they can be math operands. For example, subtract two dates to find the number of days in between.

Although Excel records dates and times as serial date values you don?t have to enter them that way. You can manipulate dates and times in your worksheet formulas just as you manipulate other types of values. You enter date values in formats that Excel automatically applies. To enter date values in this way, type the date in one of the following formats: d/m/yy, d-mmm-yy, d-mmm, mmm-yy . You can also enter 4-digit years for any of these formats. If your entry doesn?t match any of the built-in date or time formats, Excel picks the format that?s most similar to your entry.

You can also enter times in a time format. Select a cell and type the time in one of the following forms: h:mm AM/PM, h:mm:ss AM/PM, h:mm, h:mm:ss , or the combined date and time format, m/d/yy h:mm . Notice you must separate the hours, minutes, and seconds of the time entries by colons. If you don?t include the AM, PM, A, or P with the time, Excel uses the 24-hour (military) time convention. In other words, Excel always assumes that the entry 3:00 means 3:00 AM, unless you specifically enter PM .

You can create an evenly spaced series of dates in a row or column in several ways, but the job is especially easy when you use the Fill handle. Suppose you want to create a series of dates in row 1. The series begins with March 1, 2002, and the dates must be exactly one month apart. If you enter 3/1/2002 in cell A1 and drag the fill handle to the right, Excel extends the series of dates incrementally by days. After you drag, Excel displays a smart tag adjacent to the selection. Click the smart tag to display the smart tag action menu, which displays a number of Autofill options; select Fill Months to convert the already-extended day series in to a month series.

If you drag the Fill handle by right-clicking it, a shortcut menu that is similar to the smart tag action menu appears. You can use this shortcut menu to select a fill command before performing any fill action. If what you want to do isn?t represented on the menu, click the Series command at the bottom of the shortcut menu to display the Fill Series dialog box. You can use the Series command to tend a series of dates with a bit more flexibility than using the Fill handle. To use this approach, type the starting date, select the range of cells you want to fill (including the starting date), and choose Edit, Fill, Series to display the Fill Series dialog box.

You can also perform logical and text operations. The & operator connects two values to produce one text value. Comparison operators, which include =, <, >, >=, <=, and <>, compare two values and return the logical value TRUE or FALSE .

By default, Excel uses relative references. An example of this is below. To compute the totals for leather chairs and hardwood desks, you can copy the formula in cell D2 to cells D3 and D4. Use the Copy and Paste buttons on the Standard toolbar, or drag on the AutoFill handle of cell D2. You will see that the cell references will automatically adjust for the new location. For example, the formula in cell D3 will be =B3*C3, correctly reflecting the total for leather chairs. This automatic adjustment applies when you copy or move formulas with relative cell references.

For further clarification: if you were literally copying the formula in D2 down the worksheet, the formula in each of the cells D3 and D4 would B2*C2. But again, relative references make the formula in D2 analogous to "multiply the 2 cells to the left of me together and return the value here." So, when you copy this formula down to D3 and D4, you get what you hoped for.

If you need to copy a cell reference exactly as it appears in the original formula, then you must use absolute cell references. An absolute cell reference has a $ sign preceding the column letter and row number. In this example, we anchor cell C15 as absolute so that no matter where we fill or copy D6's formula, C15 will remain anchored.

You can also use mixed references, such as $A1 or A$1. When you copy a formula with a mixed cell reference, the column or row (whichever one does not have a $ sign) automatically adjusts for the new location while leaving the other part of the reference unchanged. As shown in the example, before copying the formula for January totals to calculate the February totals, first make the reference to column B absolute so that the correct unit price multiplies the February order quantity: your formula for D3 would be $B3*E3. Copy this formula to F3, fill down, and you are good to go.

The AutoSum button on the Standard toolbar is a shortcut for creating a formula that totals values in a range of cells using the Excel SUM function.

For example, look at the Blue Sky Airline Sales Report. To compute total January sales in cell C9: click in cell C9, then click the AutoSum button (note that Excel gave the correct sum range, C5:C8), and then press Enter or click the Check button on the formula bar. To total sales for each month all at once, select the range C9:E9 before clicking the AutoSum button. To compute monthly totals in row 9, regional totals in column F, and the grand total in cell F9, select the range C5:F9 before clicking the AutoSum button.

In proposing a sum range, Excel assumes that you are adding values down a column or across a row. If the proposed range is incorrect, just select the right range by clicking and dragging and then press Enter . The formula =SUM(C5,D8,E7) adds 10111, 21500, and 16900 while the formula =SUM(C5:E5,C7:E7) totals the north and east region totals.

The latest addition to the functionality of the AutoSum button is the menu that appears when you click the arrow next to the button. You can enter the Average, Count, Max, or Min function almost as easily as you can enter the Sum function?all it takes is an extra click to select the function you want from the menu. Plus, the More Functions command opens the Insert Function dialog box, where you can access any Excel function.

To create a formula that begins with an Excel function, select Function... from the Insert menu or click the Paste Function button (below) on the Standard toolbar.

Excel inserts an = sign to begin the formula and then brings up the Paste Function dialog box. To insert a function elsewhere in the formula, select Function... from the Insert menu or click the Paste Function button on the Standard toolbar or the Formula Bar .

In Step 1 of the Paste Function , select the function by clicking on its name. If you do not know the name of the function that you need, select the Function Category that it falls under to filter the Function Name list. Every time you select a function name, a description of the function and its arguments appears. For more information on the function you selected, click the Help button on the Paste Function dialog box. This brings up the on-line help topic window for that function.

Once you've selected the function, click the OK button to move on to Step 2. In this final step, you fill in the required arguments in the edit box(es) provided and click OK when you're done. For the arguments, you can type values, select cell ranges, or select a name you previously defined. You can also enter a formula (without starting with an = sign) as an argument. If you want to enter a function in the argument (this is called a nested function), click the drop down menu where the Name Box usually is and select More Functions . You will need to complete the steps of the Paste Function for the nested function before completing the original function. To the right is an example of the second step in the Paste Function tool.

For those of you using Excel XP, the Paste Function is now called the Insert Function . The Insert Function works very much the same as the Paste Function. When you want to use a built-in function, click the Insert Function button?the fx button located in the formula bar. (You can also choose Insert, Function from the menu bar.) When you do so, the Insert Function dialog box appears and it operates in the same manner as the Excel 2000 version.

The formula that computes average January sales for Blue Sky Airlines is =AVERAGE(C5:C8) . If the range C5:C8 were named January, then the formula =AVERAGE(January) produces the same result.Here are additional examples:

Normally when you copy a cell that contains a formula, the formula is pasted as well, which is handy. But if you want to copy only the results, without the formula, choose Edit, Paste Special . The Paste Special dialog box appears. Among many other things, you can choose Paste Special to extract the results of formulas. To transfer only the resulting values of formulas, select the Values option.

In Excel XP you can bypass this step by using the Office Clipboard on the Task Pane . First, go to Edit, Office Clipboard to activate the Office Clipboard. Then click and drag through the results you wish to paste. The values will automatically be placed on the Office Clipboard. To paste only these values, go to your desired cell and then simply click the values on the Task Pane. You can paste these values as many times as you like as long as they are still on the Office Clipboard.