Select TypeLib Information in the Project References tab and paste the following code into form_load, this gets the GUID for stdole2.tlb so just change the path to your DLL. You can use this object with a prog id (i.e. "Excel.Application") but I can't remember off the top of my head how to do it but there is info on this on msdn online, just search for TypeLibInfo

Private Sub Form_Load()
Dim objTL As New TLI.TypeLibInfo ' Info obj about type library
objTL.ContainingFile = "c:\winnt40\system32\stdole2.tlb"
Debug.Print objTL.Guid
End Sub