The user inputs values into column B, starting in B1. The number of
values varies from a dozen to several hundred. The values are
typically copy/pasted from another spreadsheet.

Cell B500 counts the number of values the user entered, with COUNTA
(B1:B499).

I need a msgbox or error message to appear if B500 does not equal a
number in C500.

The usual Validation tool in the "Data" menu works fine IF the number
in B500 is input by the user. If the number in B500 the result of a
formula, though (i.e. COUNTA), the validation doesn't work! Seems like
you can't have a calculation and a validation in the same cell....

So I was trying to write an IF formula that would trigger a msgbox
saying "the number of values entered is not correct" if B500 doesn't
equal C500.

Something like:
= if(B500=C500,"",msgboxmacro)

No luck. Dead as a doornail. Can somebody please help? Surely there's
a way to do this. I need SOME way to alert the user to the fact that
the number of values entered doesn't equal the number in C500.

Thanks. Please reply to the newsgroup.

Bill S.