>I've determined that it may not be possible to use the DLL from VFP. In researching it, I discovered that some of the function require the address of a callback function. While this capacity is available in VB, it is not in VFP. Sorry.

Oh what a pity! Don't mind George, you have done as far as you can, anyway I found another DLL's that run much better than this one (they have also disk spanning,...) these are the one that EasiZip is build (http://freehosting2.at.webjump.com/698c419ca/ea/easyzip-webjump) the source DLL's and sample Delphi :( code are located in http://www.geocities.com/SiliconValley/Orchard/8607/main.html, can you take a view to this? Thanks.