However, it's treating the A7&B7 as a literal, by inserting apostrophes: 'A7'&'B7'
That's preventing the lookup from working. How can I tell it that A7 and B7 and cells in the spreadsheet, and not literals?
After executing this line of code, switch back to Excel, click in the formula bar (the whole formula should be selected), hit Ctrl-C to copy it, hit Esc to get out of edit mode, and paste the result here. That is, what is the formula that the cell ends up having?