If a formula is retrieving data from the wrong cells, it's never going to calculate the right result. By tracing a formula, you can see all the cells that a formula uses to retrieve data.

Any cell that supplies data to a formula is a precedent. To trace a formula, follow these steps:

1. Click a cell that contains the formula you want to check.

2. Click the Formulas tab.

3. Click the Trace Precedents icon in the Formula Auditing group.

Excel draws arrows that show you all the cells that feed data into the formula you chose in Step 1, as shown in Figure 8-15.

4. Click the Remove Arrows button to make the auditing arrows go away.

Figure 8-15:

Excel draws arrows that trace precedent cells that feed data into a formula.

Finding which formula(s) a cell can change

Sometimes you may be curious how a particular cell might affect a formula stored in your worksheet. Although you could just type a new value in that cell and look for any changes, it's easier (and more accurate) to identify all formulas that are dependent on a particular cell.

Any formula that receives data is a dependent.

To find one or more formulas that a single cell might affect, follow these steps:

1. Click any cell that contains data (not a formula).

2. Click the Formulas tab.

3. Click Trace Dependents.

Excel draws an arrow that points to a cell that contains a formula, as shown in Figure 8-16. This tells you that if you change the data in the cell you chose in Step 1, it will change the calculated result in the cell containing a formula.

4. Click the Remove Arrows icon in the Formula Auditing group to make the arrows go away.

Figure 8-16:

Excel can identify which formulas a particular cell can change.