Try limiting the value to a date.

And make sure it's less than 10 (for 240 hours) or 20 (for 480 hours) (or
whatever limit you want).

Then try entering some of those values.

Post back with the entries that failed that should have been ok and the ones
that were accepted that should not have been.

Robert Crandal wrote:

Hi again everyone....

I am currently using the following custom format:

[h]:mm

How can I use data validation to prevent invalid
data from being entered into a cell of that format??

For my purposes, I only want data which consists
of 1 or more digits in the "hours" field, folowed by
one colon, followed by 1 to 2 digits in the minutes
field.

Do I need to enter some sort of formula into the
data validation field??

thank you!

--

Dave Peterson