Hi Richard: I think you need fire the onchange event, in the select tag ( whit _onchange="yourJSFunction();" if using SELECT helper) May be you can see this slice ( http://www.web2pyslices.com/slices/take_slice/144) and the working sample app: http://ochiba.fluxflex.com/Ajax_Cascading_Drop_Down/default/index
HTH Bye
