There is not “if, then” structure in Endnote. – I would put the 1-10 in the cited pages field when you wanted that to show up. – However, how does a reader distinguish what you are intending? Usually the full page numbers are given in the full reference at the end, and no page numbers are given in the citation, unless you wish to highlight a subset with the “cited pages” functionality. That is what Endnote supports.