IF function to stop 401k match at 1500 if False

I'm trying to create a IF function to stop at $1500 for 401k employer match. To make it simple the variable in column D is constant but in reality it's based on 50% match amt up to $1500 of amount contribute(% of gross pay). The accumulation of matching is a rolling balance. If the match amt is less 1500, then match amt. But False, the left over amt equal 1500 then STOP there onward.



IF(SUM($D$3:D19)+($C20*0.5)<1500,$C20*0.5,SUM($D$3:D19)+($C20*0.5)-1500)