Hello Conorg and Welcome to Excel Forum.
Try pasting the following formula into cell H4 then drag the fill handle over to AA4, and while H4:AA4 are still selected drag the fill handle down to AA7: =IF(AND(H$2>$E4,H$2<=EOMONTH($E4,$G4*3)),"Void", $F4/4 )
Let us know if you have any questions.