Last year I have downloaded VFP sample FoxproExample.zip from http://www.idautomation.com/foxpro/ for a adhoc project. Fit into my project with almost no changes.

*********************************************************************
*
*  Visual FoxPro Functions for Bar Code Fonts 2.11
*  Copyright, IDAutomation.com, Inc. 2000. All rights reserved.
*
*  Visit http://www.BizFonts.com/vba/ for more information.
*
*  You may incorporate our Source Code in your application
*  only if you own a valid Multi-user, Corporate or Distribution
*  license from IDAutomation.com, Inc. for the associated font and
*  the copyright notices are not removed from the source code.
*
*  Distributing our source code or fonts outside your
*  organization requires a distribution license.
*
*  To find a particular function, search the text for it.
*
*  HOW TO USE in Visual FoxPro:
*  For best results, just add this file as a program module
*  to your VFP project, set it as a procedure file using
*  SET PROCEDURE TO .. ADDITIVE command
*  somewhere in the main (startup) code of the project
*  and access the function in your application as necessary.
*
*  To do this, rename this file to IDAutomationVBA.PRG
*  Then, in your VFP project manager select "Code" pane,
*  press "Add..." button and select this file.
*  Then put following command in the startup code of your application:
*  SET PROCEDURE TO IDAutomationVBA.PRG ADDITIVE
*
*  Example (type in command window):
*     SET PROCEDURE TO IDAutomationVBA.PRG ADDITIVE
*     ? Code128b("123456789")
*
*********************************************************************

...

procedure Postnet
    lparameters pcDataToEncode, pnReturnType
    * Copyright é IDautomation.com, Inc. 2001.  All rights reserved.
    * For more info visit http://www.BizFonts.com or http://www.IDautomation.com
    *
    * The purpose of this code is to calculate the POSTNET barcode
    * Enter all the numbers without dashes

    m.lcDataToPrint = ""
    * Check to make sure data is numeric and remove dashes, etc.
    m.pcDataToEncode = chrtran(m.pcDataToEncode, ;
        chrtran(m.pcDataToEncode, NUMCHARS, ""), "")
...