I think I understand the basic problem. You need a Multiple choice field which is populated with the employees associated with that user.
Look here for some details/examples.
Basically you want something like this, this example doesn't do everything but I hope it's a start.
class SimpleForm(forms.Form):
employees = forms.MultipleChoiceField(required = False, widget=forms.SelectMultiple)
def __init__(self, *args, **kw)
user = kw.pop('user') # you need to pass user to into this function as a kw argument
super(SimpleForm, self).__init__(*args, **kw)
# this asssumes the user as a field (or related field reference) to employees
# either way somehow you need to execute a query which gets the users employees.
self.fields['employees'].choices = user.employees.all()
def save(self, *args):
# if employees is empty set them all to selected