>Form that is accessible to users with different security Rights.
>How to control field level security on your forms?
I would say, create a function that check for access rights in the object's WHEN method. Perhaps something like...

FUNCTION CHK_ACCESS
PARAMETERS table_field
RETURN(SEEK(login_id+table_field,'SECURITY',login_field) and SECURITY.ACCESS)

where you have a table called SECURITY that has fields for login_id, table_field (i.e. "anytable.fieldname"), and access (.t. or .f.) indexed on login_id+table_field TAG login_field

In your WHEN method
RETURN(CHK_ACCESS(THIS.datasource))