How to capture the search expression entered by user and then add with the search spec expression i

I am having trouble in capturing search Exp entered by user in real time in pick applet. Basically I am filtering record on pick applet based on eScript but it fails if user wants to further filter down the records from the displayed list. What i need to do is capture the search expression entered by user and then add with the search spec expression i am using in script. However I am unable to capture what user is entering from the pickapplet