You would need to implement user-level security. This is not for the faint of heart. Microsoft has a FAQ on this subject. You will need to read it, read it, and read it.
One other option would be to have different screens for different users. You could password protect the forms. Therefore, if UserReadOnly clicked on frmRead a password would have to be entered. You could set up the forms so access would be read-only. I'm not really sure what you are trying to do so this may not be a good suggestion. For absolute control you would need user-level security.