There are ways to close an open workbook but if you want toclose all the open workbooks, you can follow below approach:-
Hold the Shift key while displaying the File menu and then you will find “Close All” option on the menu. Choose this, and all our workbooks would be closed.
You will, of course, be prompted to save changes on each open workbook, if necessary.
Note: This only works if we hold down the Shift key when displaying the File menu. This applies to Microsoft Excel versions: 97 ,2000 , 2002 & 2003
Nice Tip.