Many of us have built related select controls, forms with two (or more) drop down
Select Media Type:
The form contains two controls, one named “mediaid” and the other named “artid”.
“mediaid” is bound to cfc:art.getMedia(), and so to obtain the list of media types to populate the control, the client makes an asynchronous call to the getMedia method in art.cfc, and populates the list with the returned array. As we’d want this control to be automatically populated when the form loads, bindonload is set to “true", this way the getMedia() call is fired automatically at form load time.
This example binds just two controls, but this mechanism can be used to relate as many controls as needed, and not just controls either.