Limiting fill values in a formula

In a cell, I have the following formula: =(B2*E1+B2)-G1. I want to autofull by dragging that cell downwards, but I only want the B2's to auto increase, while keeping E1 and G1 the same.  For example, instead of =(B3*E2+B3)-G2, then =(B4*E3+B4)-G3, etc., when what I want is =(B3*E1+B3)-G1, then =(B4*E1+B4)-G1 etc.