It sounds like the issue is with using cell references as criteria in the SUMIFS formula. One solution could be to use the INDIRECT function to convert the cell reference into a cell address that can be used in the formula.

Here's an example of how you could modify the formula using the INDIRECT function:

1. =SUMIFS(G2:K2,$G$1:$K$1,"="&
   Code:

   INDIRECT("M12")

   ,$G$1:$K$1,"<="&
   Code:

   INDIRECT("M15")

   )

This formula should work as long as the values in cells M12 and M15 are valid cell references. The INDIRECT function will convert the cell references into cell addresses that can be used in the SUMIFS formula.