That's a risky idea if, as it sounds, you want the BarCode TextBox to be a bound control of your form. How would the operator use it both to select a new item as well as update an existing one (which is after all the natural expectation of a user in those circumstances)?
What is a sensible approach is to create a separate, unbound TextBox (possibly in the Header section of the form) which is used specifically for selecting the record to navigate to. In such a case you would need to make sure you handled the possibility that the user navigated away from the current record without saving any existing changes.
Basically though, in the AfterUpdate event procedure of this new TextBox (we'll call txtBCNav for now) you would have some code to navigate to the correct record, or go to the new record if no matching one were found, and ensure the BarCode TextBox had the value already defaulted to the value from txtBCNav (Only required for New records of course).