how to group numbered references X3 Word-Mac

I put new references in a document that already have some and now I have something like this…

…is a bad prognostic factor (9)(18)(21)

how can I change this for

is a bad prognostic factor (9, 18, 21)

I tried manually but every time I insert a new reference go back to the inicial format.

Thanks a lot

Regards

Output Style? 

I suspect you may have spaces between the individual inserted refs.  If you remove those carefully, reformat and it should combine them. 

Since I am new using Endnote can you please describe how I do this procedure?

I just have to put the numbers whiout space (eg  (9)(8)(10) …) and them? How I reformat?

Thanks a lot

Regards

If you add another reference, it will probably fix the others automatically.  - Otherwise, it should be an Endnote toolbar option in Word - I am not too familiar with Mac Word tools.  It is probably called “format bibliography”  or “format paper”?   This will take you to a window which lists the current Output style selected for that manuscript, and just say OK.  You can explore some of the other options available there, for fun.