Excel 2007
  1. Select the Windows button in the upper left hand corner of Excel 
  2. Select the Excel Options button 
  3. Select the Add-Ins tab 
  4. From the Manage dropdown, select COM Add-in and select Go 
  5. Mark the checkbox beside F9 (or F9v5) and select OK
Excel 2010
  1. Select File in the upper left corner of Excel
  2. Select Options 
  3. Select the Add-Ins tab 
  4. From the Manage dropdown, select COM Add-in and select Go 
  5. Mark the checkbox beside F9 (or F9v5) and select OK
(In earlier versions, click Tools, Add Ins)