On form B. I added this formula.
I'm trying to concatenate all of values in a column named Request ID (in Form a) based on the value Description (in Form
to the Vendor Number (Form A)
=INDEX([{Request ID}]1 + [{Request ID}]999, MATCH(Description$9, {Vendor Number}, 0))
Form A
Request ID Vendor Number
123 A
125 B
126 A
Form B
Vendor Number: A
Return Value should be "123, 126"