if data exist in another table remove from drop down list

[skyhighweb]

hi it my first post and i need help with a problem.

so i have these two columns (user_id) and (tagged_id)
table name is bids.

name are selected from user_id and inserted into tagged_id.

how can i make the name selected from the user_id not show up in list anymore.

for example on the list are
steve
mike
dave
moses

if someone select dave it get inserted into tagged_id i dont want it to show up on the list anymore. hope u understand.