=SUM(IF(ISNUMBER(MATCH('tab2'!$C$3:$N$3,IF(ISNUMBER(MATCH(IF(INDEX('tab1'!$B$7:$M$11,MATCH(B11,'tab1'!$A$7:$A$11,0),0)="X",'tab1'!$B$6:$M$6),'tab1'!$B$6:$M$6,0)),'tab1'!$B$6:$M$6),0)),INDEX('tab2'!$C$4:$N$28,MATCH(B11 & C11,'tab2'!$A$4:$A$28 & 'tab2'!$B$4:$B$28,0),0)))
SUMPRODUCT ( "tab2_array"*"tab1_array") required all array should be in same dimension, but your "tab1" table and "tab2" table appear in different width.Question on the sumproduct formula. You have a reference to cell Q28 but there is nothing in cell Q28. Should that be a reference to a different cell? Thanks in advance!