When you open multiple Excel 2013 workbooks, each workbook opens in a separate window but in the same copy or instance of Excel. There may be times when you want to open the second or third workbook in a new instance of Excel. For example, while you're running calculations on a large workbook, and you want to work on a different workbook.
Here's how you'd open another instance of Excel to view the second workbook:
Right-click the Excel icon from your taskbar.
While pressing Alt, click the workbook you want to open from the list.
You might also like to know how to automatically open a specific workbook or template when you start Excel.