Hi
What I would do faced with that is to build a Select statement for all the known types that may be passed (assuming you do not plan on using dozens of types).
Select Me.Tag.GetType
Case GetType(System.Security.Cryptography.X509Certificates.X509Certificate2)
' ...........
Case GetType(System.Security.Cryptography.X509Certificates.X509Certificate2Collection)
' ...........
End Select