Assuming you are using Excel 2007 or a more recent version, you should be able to create up to 64 nested IF functions. It's possible that you're not using the IF function correctly, so you might want to revisit the video and e-book for Expert Skills Lesson 3-5: Use the IF logic function for a refresher.
You'll notice that this lesson recommends against using nested IF functions, and instead recommends placing single IF functions in many separate cells. This often makes the formulas easier to work with.
An alternative that you might want to consider is the CHOOSE function. This allows you to display various different values depending upon a single cell that contains a number.
=CHOOSE(A1, "X", "Y", "Z")
...would look in cell A1 and display "X" if the number 1 was found, "Y" if the number 2 was found, and so on.
For more about the CHOOSE function, try searching for it in the Insert Function dialog.
For full instructions on opening the Insert Function dialog, see Expert Skills Lesson 3-3: Use the Insert Function dialog and the PMT function.
If you're still having trouble getting this to work, please attach an example workbook and I will try to provide a solution.
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