Troubleshoot Long Formulas
How many times have you had long formulas that didn't give you the answer you were looking for? Sometimes it can be difficult to determine where the problem is.
Here's a tip I use when working with long formulas.
In the Formula Bar (the white area directly above the column headings and to the right of the equal sign) drag the 'I-beam' cursor to select part of the formula. Then press F9.
When you do this, only the selected portion of the formula is evaluated. This will help you determine which part of your formula is the problem.
IMPORTANT! When you're done, remember to hit the ESC key to get your original formula back. If you accidentally press Enter, your formula will now include the evaluated portion as a fixed value. You'll have to use Edit, Undo (CTRL+Z) to get back to your original formula.