Can only select a drop down option once

I can't see any of your code so i've no idea what you did to copy it.

Also i dont know what helper columns mean.

Something similar but slightly different. Each player needs a list with the clubnames that remain available to him. These lists can be found in columns AA, AB, etc. Such columns can be called helper columns. The list for Dave is a named range "Dave", etc.., press ctrl+F3 to see a list of these named ranges.