What you are describing is called a conditional value list. You need a value list that only lists employees where the value in that radio button indicates that they are still "active" employees. For this example, I will assume that the radio button value for an active employee is just that, the word "active". You'll need to modify things to use the actual value in your radio button field and to use your field names for mine.
Define a calculation field in your employees table, cActiveEmployee as:
If ( YourRadioButtonField = "Active" ; EmployeeName )
Define the value list for your check box field to list employee names from cActiveEmployee instead of EmployeeName.
(also the two tables are not related, they just use the same field records?)
Sorry, but that makes no sense. Without a relationship, they cannot "just use the same fields" and a "field record"?? does not exist in FileMaker.
maybe a better way of saying it would be that they are not related but i have used the employee names as a value list?
I have tried to follow the above instructions but it has not removed the inactive staff from the list and when i tried to move an active member of staff to inactive in the employee table it now tells me 'This action cannot be performed because this field is not modifiable.'
I'm sorry i am so thick. the instructions look pretty straight forward...
Open Manage | Value Lists
Create a new value list.
Select the "use values from a field" option.
In the drop down at top left, select the Employees table.
In the list of fields shown underneath, select the cActiveEmployee field.
Click OK until all your dialogs have closed.
On your layout, keep your original field on the layout, but update it in the Inspector to use this new value list as the values that appear as check boxes in the field.