From Integrated Software Design:
On-Tap PostScript for Windows lets you add bar codes to output from any application software that supports PostScript printers. On-Tap PS turns PostScript printers into bar code printers. With On-Tap PS you can print bar codes from your existing application in minutes. Simply place a special trigger character before and after the information you'd like to bar code. When you print, bar codes appear in place of the information that you have marked.