use this formula
=IF(OR($B2=DATEVALUE("31/12/2099"),AND(DAY($B2)>=15,OR(DATE(YEAR($B2),MONTH($B 2),DAY(1))>=DATE(YEAR(D$1),MONTH(D$1),DAY(1)),DATE (YEAR($B2),MONTH($B2)+1,DAY(1))=DATE(YEAR(D$1),MON TH(D$1),DAY(1)))),AND(DAY($B2)<15,DATE(YEAR($B2),M ONTH($B2),DAY(1))>=DATE(YEAR(D$1),MONTH(D$1),DAY(1 )))),0,$C2)