>>Ok, I was asked to build a dll that can
>>be accessed from a VB program. I built
>>a custom class that has the required code.
>>I marked it as olepublic. I put the class
>>in a project and then built a dll (I chose
>>single threaded). It built a dll file. I
>>wanted to test it from VFP so I ran a
>>program that does a set library to that dll,
>>additive and I get an 'Invalid dll' error.

What you're building isn't really one of the "API-style" libraries but rather a COM object. Register the DLL and use CreateObject("MyNewDll.WhateverClass"). If the code is in the Init you can pass parameters as well (for lost of reasons, I'd recommend against putting it in the Init, though - instead I would have a separate method).