In the PI-SDK 1.1 release, the NamedValues collection has been extended to add the ability to remove NamedValue objects. As an existing interface can't be changed, a new interface, INamedValues2, has been built which inherits from _NamedValues - thereby supporting all the features of the original interface - and contains additional methods (extended interface). For backwards compatibility, the NamedValues collection, supports both the old interface _NamedValues and the new interface INamedValues2. Likewise the NamedValue object has a new "extended" interface, INamedValue2, which provides Rename and Detach capabilities.
In general, secondary interfaces cannot be accessed from VBScript. This is because VBScript is a typeless language and does not support the Dim statements As <type> clause. However, extended interfaces as described above are accessible from VBScript because the new methods have been added to the IDispatch interface, which is all VBScript, can see.