Hi Mark ,
I am not clear on what you want to do. What is the data that is present ? If it is data of type date , e.g. 3/17/2012 ( March 17 , 2012 in the mm/dd/yyyy format ) , then it can be formatted as a number , or as date in any of the several date formats. If it is text that we would recognize as a date e.g. Dec. 12 , then changing the format to date or number will not really change anything , since Excel recognizes Dec. 12 only as text.
Narayan