Setting Focus() to a desired field of a table in an expandable Livecycle Designer forms

This is what I am trying to accomplish:
 
1. There is an expandable Livecycle Designer form
2. One of the form field ("itemName") in this form is filled when a scanner scans a barcode
3. As soon as the item is scanned, two actions happen in the form
a. All the other related fields in this form are calculated/populated
b. An line is added at the end of this form to scan the next item.
 
Challenges I am seeking answer for:
 
1. When the item is already scanned, the cursor in the form should focus to the itemName field in the newly added line. This is needed as every time an item is scanned, the user will not have to set focus manually (using tab or mouse).
2. Second challenge is that the length of the barcode is not fixed, so a 'full' functionality of the form action can not be used.
3. Third challenge is that the form registers every entry of individual barcode digit (for one scan) as a change. This makes it hard to use change functionality of the forms as a viable option. (Example: while reading barcode 12345, the form registers five different changes (should be one)).
 
Everything else has been taken care of in this application, except setting right focus. Any help with set focus will be deeply appreciated. Thanks.