Sum-if-product formula

[Steve]

Hello. Does anyone see anything findamentally wrong with this
formula?

=SUMPRODUCT(--(MPD!$B$2:$B$18000=CONCATENATE(I$2,$B27)),OFFSET(MPD!$A
$2:$A$18000,0,MATCH(I$4,MPD!$B$1:$CB$1,0)),MPD!$CD$2:$CD$18000)

I want it to look in column MPD column B, determine if that ceel meets
the criteria of Concat I2, B27. If it does, sumproduct MPD column CD
and the column on the MPD sheet where, on row 2 of the MPD sheet, the
contents of Sheet1 Cell I4 match.

Thanks!