In your example, on Sheet1 C5
=MAX(IF(TEXT(Sheet2!$F$5:$I$5,"mmmm")=C$4,Sheet2!$F$5:$I$5,0)) (CNTRL SHFT ENTER)
It is an array formula so requires CNTRL SHFT ENTER instead of ENTER
You'll need to spell February correctly for it to work.