If the two Excel workbooks have the same name, you cannot open them at the same time. For this, either close one of them and then open the other or change the name of one of them.

How to Compare Two Excel Spreadsheets for Duplicate Rows. Excel 2013 can locate duplicate rows as long as one column contains a unique identifier for each record, such as a product ID or account ...

The ability to automate tasks in Excel for the web has been a long wait—but it’s finally here, and it was worth the wait.