Assign Employees To Task Then Remove Employee From List Of Available For Other Tasks

I need the ability to assign employees to a different task in each of four different timeslots on a daily basis. What I would like to do is as I assign an employee to a task in timeframe 1, I would like for them to become unavailable to assign to another task in the same timeframe.

For Example: Three employees to assign to three tasks at the 8 AM to 10 AM time slot.

Employee
Task
Time
Assigned

Emp 1, Emp 2, Emp 3
Task 1
8 AM to 10 AM
Emp 2-Task 1

Emp 1, Emp 3
Task 2
8 AM to 10 AM
Emp 3-Task 2

Emp1
Task 3
8 AM to 10 AM
Emp1-Task 3

It would be nice to set this up in a form where my person doing the scheduling can assign an individual to a task and that individual name disappears from the combo boxes, list boxes, or is "greyed-out" in a listing of employees available for the time period for the remaining assignments.