在VB6中，如何调用需要指向对象的指针的COM对象？

I'm having trouble with a .NET Assembly that is com visible, and calling certain methods from VB6. What I have found is that if the parameters are well defined types, (e.g. string), calls work fine. If they are higher level objects, it raises a runtime error '438' suggesting that the property or method is not present. I suspect that this is a question of having the correct signature on the call, but I can't see how to do this correctly.I'm having trouble with a .NET Assembly that is