Tests the value of an expression to determine whether it has the OLE value V_IUNKNOWN.
IsUnknown ( expr )
expr
Any expression.
The IsUnknown function returns True (-1) if expr is a Variant and the value of expr is V_IUNKNOWN. This value may be returned by a call to a property or method of an OLE Automation object. Otherwise IsUnknown returns False (0).