A) Yes - This can be easily done. Simply wire-up each RadComboBox to call the same client-side JavaScript function. This works the same as wiring up one RadComboBox, only you only have one function and you also use the same function name on the declarative code.
B) This is also simple. The footprint of the JavaScript function is: function functionName(sender, args);
When the JavaScript function in invoked by a RadComboBox, it includes a reference to itself. In other works, the sender parameter always points back to the control that invoked the function, in this case a RadComboBox.
Thanks for the reply. I did get that far but I am trying to replace some dropdown controls in a third party software package and it doesn't like what I'm doing to it :) I am trying to revert and see where it's breaking. Again, thanks for the input.