olly,

Post one of the formulas that you're using and we can probably give you
a better answer.
From what it sounds like you're trying to do, you have a vlookup
formula in B1. You could use something like this in B1:
IF(C1="","Please Fill In Col C",your vlookup formula)

John

Olly wrote:

Hi
I have 3 adjacent cells. What i want is, for example, a
way of ensuring that, if there is data present in cell A1
(which looks up data and places product code in B1), then
the user cannot leave cell c1 (order number) blank. The
problem i envisage is that cell A1 looksup product codes
from sheet 2 and places them in B1, so i'm thinking that
any formula to ensure c1 isn't blank must ensure that if
the lookup doesn't find the relevant cell (i.e. a1 isn't a
valid product code and so throws up the messahe "n/a" in
B1) then cell C1 should not be required.

Can anyone help me out here?
Any help greatly appreciated
cheers
olly