Hi
I can help on the client side, but havnt done this on the serverside.
I guess you must be creating the rddl on the fly, if so then add an attribute for the onchange like so. Note that on IE you use one method and firefox another as it renders differently on firefox.
Dim rddl As New CuteEditor.RichDropDownList(Editor1)
IE version
rddl.Attributes("onchange") = "BLOCKED SCRIPTalert(this.GetValue());"
FireFox version
rddl.Attributes("onchange") = "BLOCKED SCRIPTalert(this[this.selectedIndex].value);"
Hope this helps