Ajax postback with cascading dropdowns

[mfunai]

Can anyone help me with this? I have 4 cascading dropdowns and I need to postback to my code behind on the last one to get data to fill my datagrid. I've tried to set autopostback to true but it keeps reloading the dropdowns and flashing my page, over and over again. When I set it to false I don't get the postback and I've tried to add a trigger to do an asyncpostback but couldn't get that work either. Any ideas how I can do this?