Convert Numbers to Words
The following is a picture of a spreadsheet using a Formula to convert a number to words:

You can find directions and the code to use this UDF in the Knowledge Base at:
http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q213360
If the link quits working you can also find a copy of the code at the original place I saw the tip:
The Planning Deskbook: Converting Numbers to Words


I put together some links about this problem:
Numbers to Words
I like John Walkenbach’s discusion of the cardinal number function that is built into Excel:
=BAHTTEXT()
Thanks for both the links Doug.