Dimishing drop down

[Bananna1]

Hi
I have a parking rota with 4 spaces available every day. I am putting a sheet together with dates down the side and names across the top.
I want people to pull a drop down and click on '1' to reserve a space on their chosen day(s). As a '1' is clicked on, it should disappear from the drop down for that day, leaving only 3 more '1's until all the spaces are booked and the drop down is empty.
Can anyone help me?

[shg]

See http://www.contextures.com/xlDataVal03.html

[DBY]

Along the lines of shg's suggestion, you could use a single Validation List formula with some Conditional Formatting, a little hard to explain in a few words but maybe the attached file will give you a few ideas.

DBY

[Bananna1]

Thanks so much - that's really helpful