How would I go about generating Visual Basic 6 Proxy dll/tlb from a WSDL file?
Similar to the WSDL2Java for java, but for Visual Basic.
You could generate a Web Service client proxy using one of the tools available in .NET, either through Visual Studio or one of the command-line programs (wsdl.exe when using ASMX or svcutil.exe when using WCF) and make the resulting class and its containing assembly available to COM.
If you want a VB6 native solution, I believe your best choice is using the SOAP Toolkit.
Also, see this related question on SO:
What is the best way to consume a web service from VB6?