=SUMIFS(INDEX(INDIRECT($I7&"!1:1048576"),,MATCH($H7,INDIRECT($I7&"!3:3"),0)),INDEX(INDIRECT($I7&"!1:1048576"),,MATCH("Date",INDIRECT($I7&"!3:3"),0)),">="&DATE(K$3,K$4,1),INDEX(INDIRECT($I7&"!1:1048576"),,MATCH("Date",INDIRECT($I7&"!3:3"),0)),"<="&EOMONTH(DATE(K$3,K$4,1),0))