=IF(SUM($A$2:A2) <= 100, SUM($A$2:A2),
IF(LARGE(IF(ISNUMBER($D$1:D1),$D$1:D1),1)+A2<=100,
LARGE(IF(ISNUMBER($D$1:D1),$D$1:D1),1)+A2,"Over"))
With legacy Excel such as Excel 2013 you can apply this formula. The formula must be entered with ctrl+shift+enter as an arrayformula.