If you are talking about deleting the text boxes at a time that have been inserted to your cell of excel worksheet, plz follow the steps.
1. Open your excel sheet where the textboxes are inserted.
2. You can click one of the text box (do not click in the cell).Now press control and select the other ones with the mouse.
3. Now press the delete key and your box will be deleted.
else if you want to delete all at a time follow this.
1. Open your excel worksheet that contain text boxes. Now right click on the blank area of Menu bar (At top right corner area).
Choose Drawing tool bar if not selected. Now from the drawing toolbar (above the TASK BAR) choose the --> (arrow mark) at bottom left corner of the drawing bar.
2. Now your mouse pointer will be changed to arrow shape. Now click on the bigining of the excel sheet and drag till the page end without releasing your mouse button. Now you will see all the text boxes will be selected.(No text will be selected, Only objects will).
3. Now press delete key and all your text boxes will be deleted at a time.
Hope it works, otherwise mail mei will give you the screen shots.