I'm trying to add a package to version control in JScript that is is equivalent to doing it manually:

pkg.VersionControlAdd("OM_SW_ONE","","",true);
The outcome is no exception, and the package is not in version control (no version control icon in the project tree and error if I try to check it in/out)
I pass the 2nd parameter as an empty string as the 2nd because I don't want "Export as Model Branch" - I also tried passing undefined and null - undefined gave me a type error and null didn't work, just as the empty string.
If I pass a string as a 2nd Parameter it works - but I don't want an EAB file or the bother of making it unique.
Solutions ?
Thanks