Is it possible to have form routine execute without user pressing enter?

Hello, I have a form routine which populates a field dependent on what the user enters in another field.

FORM fillOut .
  select single barcode_id 
    from t_barcode
    into t_groceries-barcode
    where id = t_groceries-id.
ENDFORM.

I am currently using maintenance event AD.

However, the field population only occurs after the user enters the id and presses enter. I do not want this because pressing enter will create and save an entry like this:

barcode             cost                location                     id        
123123923                               california                   04

My cost field depends on the barcode being populated so what I would like is for barcode to automatically populate when id is entered so that I can fill out the cost field before creating an entry. Is this possible in ABAP?