columns D and AD in sheet 1 are formatted as text. You should format these columns as date, and if necessary, reenter data, because in AD1, there is a text: "Nov-09" !! this is just a piece of text to excel, cannot recognize it as a date...There is no way excel can recognize it as 11/3/2009...( Nov can be recognized as month 11, but the day does not appear in that text
). in you file sheet1 reatached, i reformatted columns D and AD, and reentered 11/3/2009 in AD1. You should have no errors now..
tell me if you need further assistance in automatic reformatting and reentering existing data if you have a large number of rows...