"PCLIVE" wrote...
Look at Data-Validation. Whole Number, less than or equal to, 100
....

Note that data validation is easily defeated. Copy the text 123456 in,
say, this newsgroup post, switch to Excel, and paste it into a cell
with this data validation rule. Excel will accept it without
complaint. For cleverer users, there's no way to prevent changing
formula values, e.g.,

=10+(NOW()--"2008-02-25 13:02")*1e300

Excel's data validation is weak. It can be dangerous to rely on it
exclusively. It's almost always better for formulas that use any user
entries to check those entries for validity, and return errors when
user entries are invalid.