Access control a form field in Lotus Notes

I designed a very simple Lotus Notes database with only 5 fields. I am a newbie and I don't know how to set security on one of the fields. Basically on field APPROVED I want to make sure nobody but 2 Notes users can change this field. In fact I would prefer if the other users didn't even SEE the field. There are only 2 users in my company that should ever be able to check that box, and if its not too difficult, even see that box.
thx experts...
BobR