Assuming that:

F5: A

and B5:B12 are the weights...

=SUMPRODUCT(--(A5:A12=F5),B5:B12,C5:C12)/SUMIF(A5:A12,F5,B5:B12)

Balan wrote:
I want the weighted average of selected items in an array. The items should
be identifiable by a criteria. For example if column A5:A12 has characters
A,B,A,C,A,D,E,E and columns B5:B12 and C5:C12 have some values , I want the
weighted average of columns B and C using A as the criteria. How to do it ?