I have 2 .net radio buttons on my page.

When the user clicks a button I want to change the contents/source of a drop down box on my page without doing the round trip to the server.

E.g.

If radio button 1 clicked then
call poDropDown1()
else
call dropdown2()
End if

Can anyone point me in the right direction ?
The dropdown must be populated from 1 or other of the .net methods.

Thanks in Advance