Attendance Function

Hello, i have Post type called Contact, in relation with taxonomy called event.
i need to create a custom field “Attend/Not Attend”
but this checkbox should be unique for each Event -_-
bit complicated bt can you help ?

N.B: each contact could be invited to many events.
and maybe he attend the event, and maybe no

i want to control this fields manually from admin section

https://ww.wp.xz.cn/plugins/custom-field-suite/