Triggers In Forms !!!! HELP !!!!!

Hi all,
Have written a procedure which fetches a set of values from a table...and displays these values in the corresponding fields in the form
am calling this procedure from WHEN-VALIDATE-ITEM trigger on a paricular item say First_Name .. Field First_Name has a LOV attatched to it....
My problem is i want to display the values returned from the above said procedure as soon as i select a value in First_Name (from LOV)

WHEN-VALIDATE-ITEM trigger is working fine but is fired only when i shift the focus from Field First_Name (on which it is being called) to any other field.

i want to know that from which item-level trigger should i call the procedure
such that the values in other fields are displayed as soon as i select First_name from its LOV Received on Tue Jan 15 2002 - 12:36:07 CET