Quote Originally Posted by HELPME13
If multiple X's are found, the values in B are added.
It's not clear if values in B are numeric or not - ie whether you mean to aggregate or if text strings - concatenate.

Assuming numbers - see SUMIF

=SUMIF(C:C,A1,B:B)

where A1 holds criteria be it "X" or a number.

If B holds text values (to be concatenated) then things are much messier - the approach you adopt will largely depend on volume of data etc...