What you're suggesting appears to require the table to have as many rows as there are possible choices from the dropdown, which could end up leaving most rows empty in some cases. It would be possible, however, to conditionally add rows to the table so only as many rows are created as are needed. That said, you might care to explore something like:
https://www.msofficeforums.com/word-...html#post38461, perhaps with the subsequent rows only including dropdown items that haven't already been selected.