Limit Select Fields Choices Based On Previous Submissions

Problem/Motivation

We would like to use Webform for a registration system for trade show events. We only allow so many exhibitors per exhibitor category. I would like to have a select field to select the exhibitor category. I would like to be able to set the number values allowed per each select item. The system would need to determine how many slots for each category are left by taking the overall number of slots and deducting any existing submissions from that number.

Proposed resolution

Apparently there was a module to do this in D7. It doesn't matter if it is an add-on module or a feature built into the core of Webform. I can see potential other use cases for this as a booking system. Assigning a certain amount of slots to a time block, etc.