how do I add rows to a drop down list. I am using Excel 2008

Any of this help?

• Enter the items for your drop-down list into a list on the worksheet, one item per cell. In this example, I'll assume that the month names start in cell E1 and extend down to E12, but they can be in any out-of-the-way location on the worksheet. In Excel terminology, a rectangular group of cells (such as E1 to E12) is called a range.
• Select the cell that will contain the drop-down list. If you'd like more than one cell to display the same list, just select them all now rather than setting them up one at a time. (Click and drag to select a range; hold down Ctrl while you click to select non-adjacent cells.)
• Choose Data, Validation to display the Data Validation dialog box.
• Click the Settings tab.
• In the Allow field, select List.
• In the Source field, specify the range that contains the list items. In this example, the items are in cells E1 to E12, so type =E1:E12 into the field.

http://support.microsoft.com/kb/141573

NOTE You cannot create a list in a shared workbook. You must remove the workbook from shared use first if you want to create a list.

Every column in the list has AutoFilter enabled by default in the header row. AutoFilter allows you to filter or sort your data quickly.

The dark blue border around the list clearly distinguishes the range of cells that makes up your list.

The row that contains an asterisk is called the insert row. Typing information in this row will automatically add data to the list and expand the border of the list.

A total row can be added to your list. When you click a cell within the total row, a drop-down list of aggregate functions becomes available.

You can modify the size of your list by dragging the resize handle found on the bottom corner of the list border.

http://office.microsoft.com/en-us/excel-help/about-excel-lists-HP001004433.aspx