Sub Drop Down in Table

Hi Team,

I am trying to create a table in such a way that I can have sub, sub drop downdowns.  For Example.  If I have a talbe with countries and their States and then again of the towns under those states.  I want to create the table in such a way that when I enter the State in the First feilds and go to the next one, I want the drop down to have only the states that belong to that country and then again when I go to the Towns list, I want only those towns that come up in the given state.

Please note, I know how to do the same using forms.  I want to achive the same on the table itself.

Thanks,
Sandesh.