Problem with "Soft Trigger"


I have a problem when i scan a Bar Code using the "Soft trigger", i cannot handle the callback when using the "Soft trigger".
what i need to do:
i have about 10 fields, when i open the page the cursor is set into the first input. when i click on the "Soft trigger" to scan a Bar Code, i need the cursor to move on the next field. but i cannot do this because i don't know how can i use the callback?