=IF(ISBLANK(D16),"",IF(SUM(G16-(H16+I16+J16))=0,"$0.00",SUM(G16-(H16+I16+J16)))
Is more than you need.
=IF(ISBLANK(D16),"",IF(G16-(SUM(H16,J16))=0,0,G16-(SUM(H16,J16)))
Just format the cell as $0.00, and it'll do it automagically. Blank entry will be blank. It should put what D16 is actually.
Of course I might pulling this from /dev/ass