A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Do you really mean a workbook, not a worksheet? If so, this has nothing to do with Excel. You delete workbooks with the finder. Navigate to the workbook and move it to the trash. It may still be listed in the recent files for a while, but Excel won't be able to access it from the trash. You can go to Excel preferences, general pane and uncheck show this number of recent documents to remove it from that list.