Be aware that Microsoft Excel 2013 (and higher) uses Single Document Interface (SDI) and that Excel 2010 (And below) uses Multiple Document Interfaces (MDI).
This implies that for Excel 2013 (SDI), each workbook in a single instance of Excel contains its own ribbon UI:
This raise some important issues if you want to migrate a VBA code (2010 <->2013) that interact with the Ribbon.
A procedure has to be created to update ribbon UI controls in the same state across all workbooks for Excel 2013 and Higher.
Note that :
To get more details, see the source of this example: MSDN.
This also causes some trouble with modeless userforms. See Here for a solution.