Complex VLOOK and/or Index formula question. Expert advice needed

Originally Posted by SDCh

try this on sheet Budget column F7, for copy drag across and down

{=SUM(IF(PCR!$H:$H=($B7&$C7&MONTH(F$6)&YEAR(F$6)),PCR!$G:$G))}

Note: use ctrl+shift+enter, if just enter the result will be wrong.

Excellent. This worked!! So what do those brackets do exactly? I know it has to do with an array formula...