Barcode scanning on Purchase order detail form

I want to customize purchase order line form ,when user will scan barcode new purchase order line will be created but on Prchase order detail form barcode field is not editable even after clicking on edit button.So how can I made this field edit able?

I check on grid barcode field allow edit is yes and also Its alow edit yes on datasource level so please suggest how can i get my required functionality?

Thank you

-Akhtar hassan

Business logic which resides outside of the form, may handles this. Which may found in tables & classes.
Probably placing break point in active method of purchLine datasource ,you may figure out.