Create Rule to show, in some form, if a SEPARATE workbook has been updated within X days

I am creating a dashboard in excel that pulls data from separate workbooks that are all on the same shared drive on our network. I can get data to and from workbooks as well as link to them, but I am looking to add one last dimension. At a low level, I would like to be able to show the last update/save date of the source workbook in the dashboard workbook.

At a higher level, I want to find some way to color code or add a visual cue that the workbook was updated within X days of system date, or "Today". Does anyone have any ideas how I'd pull this one off?