How do make the choice unavailable?

how do i make the form make the choice unavailable once a certain amount of people have chosen this field.

for example

Choose

check box AM

Check box PM

I want to close down the option to use "checkbox AM" once this box once 80 respondents have chosen

can you please help

how do i do this?

Yes  it is possible to achieve your requirement by taking advantage of any of the following  widgets:

Gift Registry

Quantity Gift Registry

This widget will allow you to list the options with available inventory. Once a user selects an option and submit form, the available quantity will reduce accordingly. 

Hope this helps.

Do get back to us if you have any questions.