Sorry, I missed this reply before (missing forum email notifications again…).
Did you ever get it working in the 15.9.0 final version?
If not, there really must be a way to get it working, since it’s such widespread functionality, used by thousands of applications around the world, right?!
I could absolutely help you to search for clues towards a solution if you just describe the problem a bit further here (i.e. if you didn’t already got it working in the 15.9.0 final version?).
The following info might be of value:
http://stackoverflow.com/questions/14811458/how-to-use-jscript-9-features-in-a-vb6-host
Perhaps especially the following quote?
“The undocumented ‘feature’ of the SetProperty with SCRIPTPTOP_INVOKEVERSIONING is that the value must be a VT_I4 or VT_I2 – any other integer type will be rejected as invalid.“