To expand on my previous reply....

If A1 is your data entry cell.
In B1 (or wherever) put "=IsOK(A1)"
For A1 choose Data Validation Custom and in Formula put "=B1"

My simple Test function:

Function IsOK(val) As Boolean
IsOK = (val < "") And (val < 10)
End Function

Try it out. If you enter an invalid value (=10) you will get the usual "Cancel/Retry" message.
The cell containing the validation formula would of course be hidden in the final version....


Tim.


"Guy Normandeau" wrote in message
...
You cannot modify other columns/cells inside a function call from a cell.

"Tim Williams" wrote:

Why not just put your custom function in another cell (with the entry cell as an input) and have the entry cell validation
point to
the other cell ?

Works for me...

--
Tim Williams
Palo Alto, CA


"Mat P:son" wrote in message ...
Yeah, would be nice if macros were allowed... Until that lovely day I suppose
we have to rely on the rather limited validation functionality that we've got.

Exactly how complicated is your validation? Is it still worth a try to hack
it together in the standard Excel formula language? Any pseudo-code or VBA
code available perhaps?

And although I'm sure you've been hunting high and low for info on
validation, here's a link with plenty of links that may be interesting:

http://www.mvps.org/dmcritchie/excel/validation.htm


Cheers,
/MP