But you could select C25:C29 (and maybe N21)
then use:
format|conditional formatting|formula is
=sum($c$25:$c$29)<$n$21
and apply a nice format.

But I'd use an adjacent cell. I think these are easier for most users to
understand.
=if(sum(c25:c29)=n21,"ok","Error!")

Another option would be to allow the users to enter what they need in C25:C28,
but use a formula in C29 that removes the check.

In C29:
=n21-sum(c25:c28)

AJB wrote:

I have a range of cells (c25:c29) that I want to highlight as an error when
their sum does not equal a number manually entered in cell n21. I have not
been able to figure out how to do this. Is this possible?

thanks

--

Dave Peterson