Multiple author inline referencing

How can I cite like this in endnote 6:

Ben (2001; 2008) have shown that it is possible to get help from the users forum.

I can handle it with one article; it has to be more than one article by the same author.

Many thanks for your guidance on this.

You can’t automatically.  The easiest way is the old way.  Don’t use the Author (Year) option, just hide the author for both, and type it in.  This is so rare, they didn’t make it possible I guess.