The content dialog for the barcode object lets you define the barcode more precisely. Choose "Text" if you want to print fixed text as a barcode. Choose "Formula" if you want to use a formula as a barcode, and define a valid formula expression with the "Edit" button. The formula must return a "barcode" value type. You can, of course, also enter variables. However, they must first be converted to the "barcode" type with the Barcode() function.