Display Alert/Message box when lookup field record selected/change

I am trying to perfrom an Alert pop-up box to be used with a field that is using the AJAX lookup field support. I would like when the slected value from the AJAX lookup is selected in the field to present a pop-up message box that provides additional information about the selected record. Is there an easy/supported way to do this with the AJAX lookup supported in ASPRunner? Any help is apreciated.