Creatung a record on input, then checking it on submit.

Creatung a record on input, then checking it on submit.

So I'm not sure how to do this, wondered if somebody could give me a hand. Essentially I'm trying to create a signup sheet that will be used daily.

Somebody picks what they want to sign up for, from a list, then when they submit the form it assigns them to that item. If somebody else tries to sign up for it, it will tell them that it's not available... or if it's possible, not show up as a choice? Also, if this could be related to date, so say, person A has item 1 on March 1st, then person B has item 1 on March 2. etc. Thoughts?