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How to add a drop down box in excel 2007 
Open the spreadsheet in which you want to add the drop-down box (es). 
Create a list of the items to appear in the drop-down list. 
Type the data in the order it will be displayed in the list.
The entries should be typed in a single column or row and should not contain any blank cells. To create the list of the desired items on a separate worksheet, click the tab of the worksheet in which to enter the data.