Here is my original formula
=IF(ISNA(VLOOKUP($A3,INDIRECT("'"&G$2&"'!$B$3:$I$516"),6,FALSE)),"✖",
IF(VLOOKUP($A3,INDIRECT("'"&G$2&"'!$B$3:$I$516"),6,FALSE)=$D3,
IF(INDEX(INDIRECT("'"&G$2&"'!$A$3:$A$516"),
MATCH($A3,INDIRECT("'"&G$2&"'!$B$3:$B$516"),0))>0,
INDEX(INDIRECT("'"&G$2&"'!$A$3:$A$516"),
MATCH($A3,INDIRECT("'"&G$2&"'!$B$3:$B$516"),0)),"✔"),"✓"))
Which will place an X if the value isn't found, the first type of check mark if the criteria matches and the other kind if it's found but the criteria doesn't match.
I learned today that ISERROR shortens the ISNA structure that I've built up by removing the redundant lookup. How can I use that (or something else) to shorten this formula?