Sorry for the Friday afternoon temporary brain death...
First, this code is what you really need. You need code to disable and enable fields should the employee be a full timer or part-timer. Use code like this:
If Me.chkFullTime Then
'Run these lines if employee is full time
Me.control1.Enabled=False
Me.control2.Enabled=False
Else
'Run these lines if employee is part time
Me.control1.Enabled=True
Me.control2.Enabled=True
End If
Plus, it's probably best to put that code in the control's AfterUpdate event, but also in the Form's "On Current" event. As you browse from record to record, you need those particular form fields enabled or disabled in addition to when you change them from being full to part time within the same record.
If you put the code in the On Current event, you won't need to place it in the Open event.