Please right click the text box and choose properties and select the Display tab and check the box that says limit the text box to N where N is the number of characters in your bar code. Then, check the box underneath it to move to the next field. This will let you run a rule to automatically fire the query.
You can auto insert another row in your repeating table using qRules or default values and then set the cursor to jump to that field to support scanning of multiple items at the same time. Email me if you need help with that.