Getting a Autofilled Box to be recognize by onchange

I have auto-suggest that brings down first and last name into a input box, it also brings into another input box the id of the selected item.

on that id i want to be able to auto fill a form from there.

right now i have it set up but and it auto-fills with lets say 55 but it does not execute the code to fill in the form.

however if i type something into that box it fills the form.

my question is how is it possible to have the to see eachother.

<input type="text" id="testid" name="testid" value="" onchange="showUser(this.value)" /></p>

Code (markup):

this is the input box that is being filled by auto-suggest and then i want onchange="showUser(this.value)" to execute to fill the form

 

I think you need to call showUser() inside from the auto fill function.