How do I POST to an HTTPS URL with a digital certificate

[flatlegs]

I am trying to post an XML request to a URL that requires a digital crtificate. I was provided a certificate (PFX) and imported it into my store in IE. I want to be able to post XML to the URL without having to be prompted each time to choose the appropriate certificate. I know there is a way to export the cert (CER), so I am assuming there is a way to code in the cert file location and the password to send with the post.
Any help out there?
Please be gentle, I am new at all of this and only use VB .NET 2005.

Thanks