You cant really choose what you 'submit' from the page without javascript to manipulate the form, but why do you need to do it like that?
If you just selecting employees from a list, you could just loop around all the employees in the model and create a check box for them (you may have to manually render as below - Html.Checkbox doesnt seem to work for multiple check boxes of same name)
<input type="checkbox" value="<%= Html.Encode(employee.Id)%>" name="employeeForDepartment" />
Then in your action you can do something like this:
public ActionResult Bla(int departmentId, int[] employeeForDepartment) .....
assuming that the employee id is an int. Then you can process that list accordingly (only checked employees will be submitted). It doesnt have the model binding you were using previously, but in this case, it doesnt really lend its self to processing in that way.