OFFSET formula with Variable

Hello:

I am using below formula without any problem:

=OFFSET($O660,0,MATCH(E$78,$P$3:$EG$3,0))

I need to add variable in place of $O660.
For example the above formula is in cell B3
I have B2 = 665
then i would need the above formula to become :

=OFFSET($O665,0,MATCH(E$78,$P$3:$EG$3,0))

Let me Know if you have any questions.
Thanks.

Riz