Barcode 39 generation within SAP

Our client wishes to generate a barcode 39 logic within a user-exit. This is NOT the printed output.. we just want the numbers/characters generated in the exit, then stored in a field.

I have a few questions:

1) Is this doable without a 3rd party system?

2) Is there a function module within SAP to do this?

Hope to hear from you soon. Thanks! 😊