avoiding duplicate references

I have a document that is currently grouping references cited at the same place under a common citation number (e.g. 25a-f). 

If, for example, I want to cite reference 25d (picked at random within 25a-f for illustration purposes), is it possible for this reference to be cited elsewhere in the document, without duplicating it (i.e. Endnote recognises that it should cite it as 25d and not create a completely new reference).

If this is not possible, I guess I have to cite grouped references under separate citation numbers?

I think endnote will separate and cite the record as 25d when used again later, automatically.  see image for the settings.