WinHTTPRequest[VB] & request.ServerVariables[ASP]

This is a question about communicating between a VB6 application and an asp page.

I have created an ASP webpage which checks the username and password supplied to it and responds with different content depending on the username and password. However the username and password returned by request.servervariables("AUTH_USER") and ("AUTH_PASSWORD") always return blank.

The request is being sent to the ASP site using the WinHttpRequest Object and i am using oHTTP.SetCredentials "username", "password", 0 before sending the request.

Should I be sending the credentials in a different way or should I be retrieving them in a different way?