Hi Rachel,
For specific help with validation see (look for validation)
A nice intro video usable even if you don't have broadband
http://www.datapigtechnologies.com/ExcelMain.htm
and for in-depth coverage
http://www.contextures.com/tiptech.html

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HTH,
David McRitchie, Microsoft MVP - Excel [site changed Nov. 2001]
My Excel Pages: http://www.mvps.org/dmcritchie/excel/excel.htm
Search Page: http://www.mvps.org/dmcritchie/excel/search.htm

"Gary''s Student" wrote
Checkou the Help section on Validation for a start.

"Rachel" wrote:
Is there anyway to set a warning message to pop up depending on what gets
entered into a cell?
For example if someone puts a number less than 100, can i program a pop up
to say "Warning have you though of...?"