This one is considerably more straightforward than my other question tonight...

We have a drop-down list populated by a DB lookup rule.
 

Users select an item from that drop-down list, and "Add Another" line item if needed  (table format).

Here's the problem... once a user has selected, say, "Option A..." is there a way to prevent them from seeing "Option A" again when they go to fill out their next line item?

Thanks!