In the table that contains the user accounts add a field for permissions.
i.e. 0= No access, 1=Read only, 2=Read + Add, 3=Read + Add +Edit.........
In the code for the button to open a form, use an if statement to allow opening.
If [UserPersission]>0 then
DoCmd.OpenForm "Form1"
Else
msgbox "No...