I do not know where it is in 2013, but up to 2007, I have done this using the Edit links dialog (Data tab in 2007). This dialog allows me to select a linked workbook and choose to break that link, which replaces links to that workbook with the current value. Be sure to test on a backed up copy, but, if 2013 has retained this dialog, then you may be able to accomplish this task from there.