Darga, you still didnt understood how it works in generally, read the basics on SAP Help, e.g. the stuff Hamendra has provided. Logon modules and logon pages are different concepts as you mentioned already on your own. For your requirement you dont need to change the logon module at all, if I got you right. In generally you cant have two different logon pages activated at same time at all, since you can enter only one valid logon alias on appropriate NWA configuration imho. But as I told, you can implement the logic you are talking about within the same logon page.
cheers