Thanks for your response. The array formula is a superior solution, I
hadn't considerd using an array at all.

Your post (and solution) have still left me confused, however, about
the exact nature of the problem.

"=sum() ignores text and empty cells. So if you got an error from the
=sum() function, that means that you have an
error in that range. "
AND
"Or you could change the formula that is used in the cells in
camperrev."

All the cells are empty. No formulas or values. If a value is
entered it works fine.

"And camperrev can't refer to a whole column except in xl2007. "
camperrev refers to a dynamically named range using the following
formula:
=OFFSET(Contributions!$H$2,0,0,MATCH(1E+306,Contri butions!$H:$H,1),1)

As a result, the range is only as large as the amount of entries.

Perhaps the problem is that in this case the range object returns
Nothing?