Hi,
Instead of the search GUIBB, I made use of a freestyle UIBB.
I have created a select-option screen in the freestyle webdynpro component by using the WD_SELECT_OPTION_20 standard component. This standard component will trigger an event 'ON_ENTER' upon selecting any entry in the drop down list.
Declare an event handler in the select option view controller for this event and write your respective code there.
Thanks,
Ajith