In Google Spreadsheets how do I restrict input when the number of entries for a condition are met?

Question

I am using a Google spreadsheet to gather the Registration form entries for our tournament. We can only have 10 teams per age group. How do I "close" the Registration when the number of entries for that age group reaches 10.

Answer 1

Setting up a conditional column and sheet.

Pros: quick and dirty.

Cons: you need to keep watching out if check changes fro FREE to FULL (added a conditional markup when it hits FULL ==> colored red). Logic needs tobe copied accordingly.

See example I've prepared: conditional column/sheet