Capacity for each item of dropdown list

Hi all
I have an event that create a custom field (dropdown list) in it.
Items of this dropdown are:
Group1
Group2
Group3
How can I set capacity for each Item?
For example: Number of capacity for each group is 33.
When 33 users registered in one of the groups, So other users can not register in that group and register in other groups.
best regards

Sorry Mohammad but unfortulately, Events Booking doesn't support this feature/

Regards,

Tuan