I am continuing to play with finding a solution and came across 'FILTERING' and 'LOOKUP', so I tried both - in the OTHER REFERENCES (BK730).

For LOOKUP I tried:

=LOOKUP(BK731,$G4:$G1133,$C4:$C1133)

This worked, but only returned 1 of the 13 instances where this reference (BK731) appears. I need all 13 to populate.

For FILTER I tried:

=FILTER(G4:G1133,BU731=C4:C1133)

This only returned a zero.

Still trying...