How do I detect the default Outlook profile from within Visual Basic for use with MAPI.

I have a Visual Basic application that, when executed, automatically sends an E-mail via MAPI.
The application needs to run invisibly, so I do not desire any popup windows.
The problem is that MAPI needs a profile name as follows:

MAPISession1.UserName = "doejohn"

This works great when you can predetermine that "doejohn" is the correct profile name to use.

In my case, the correct profile name to use will ALWAYS be the default Outlook profile, no matter what it is called.
So basically, can someone tell me how to detect the default Outlook profile?
I do NOT wish to use additional applications, etc.  There must be a way to determine the default profile from within Visual Basic.
This application is used on various machines, so the default profile name will likely be different for each user.

The following is a sample code snippet of what I would like to accomplish, assuming I can determine the value of strDefaultOutlookProfileName:

MAPISession1.UserName = strDefaultOutlookProfileName
MAPISession1.SignOn
MAPIMessages1.SessionID = MAPISession1.SessionID
MAPIMessages1.Compose
MAPIMessages1.RecipAddress = "someaddress@somewhere.net"
MAPIMessages1.MsgSubject = "This is the subject."
MAPIMessages1.MsgNoteText = "This is the content."
MAPIMessages1.ResolveName
MAPIMessages1.Send
MAPISession1.SignOff

Thanks, in advance, for any help.