Excel 2013 read-only file attribute problem

I have a macro that I wrote using Excel 2010 that before closing the workbook it would turn off the read only file attribute and save the workbook. I discovered that this doesn't work on Excel 2013 and produces an error because the file was opened as read-only. Has anyone got a work-around for this? I would like to keep the workbook saved as read only so other users do not alter it inadvertently. The macro reads in any new information and sets a flag indicating a save is required, then saves it prior to closing (and turning the read-only attribute back on).