I'm trying to make a last man standing football excel sheet.

This is for UK football and the idea is each person selects a football team each week, If there team wins they move onto the second week, if they lose they are out.

When you select a team for 1 week you are not allowed select that team again until the whole thing is over.

Is there a way to code into excel so when someone selects a team form the drop down menu that they can not select that team again until all data is removed ( reset )

the way i've the sheet setup is i've all the players playing the game in column A from A1 - A12
I've the word Week 1 - Week 2 etc in Row's B1 - M1 ( 12 weeks )

I've listed all 20 Up premieleage teams in column X just to have them on the same sheet so i could make the drop down menu,
I copied the dropdown menu into B2/B3/B4 for testing, But I can't really do much more without having the above setup.

So can anyone help me ?

thanks.