exposing .Net classes

I have a Visual Studio 2013 - Visual COBOL Managed (can I just refer to it as Visual Cobol .Net?) program that I am using to convert a string data type to a decimal data type, using the "convert" function (ignoring validation for now).

Currently, I have a REPOSITORY with this:

    class convertClass as "System.Convert".

and in the procedural code, I am doing this:

   MOVE convertClass::ToDecimal(myString)  TO myDecimal.

What I want to know is how to do this using the alternate approach of using the $set ilusing directive so that I can do something like this instead:

  MOVE convert::ToDecimal(myString)  TO myDecimal.

I have tried it several ways ($set ilusing"System.Convert" and $set ilusing"System"), but I can't seem to get it to recognize System or System.Convert such that I can do this.

Thanks