Need help in Excel 2007?

I have to upload a file to a server and the dates need to be in 20101231 format (YYYYMMDD), but they are currently in 12/31/2010 format (MM/DD/YYYY). I do not want to retype them all since the file has ~2000 rows. There is not an option to format date cells in this way, so I was looking for a formula or other option that may work. Thanks!