Using encoder and formatter settings on a FLASH DataSet component

I am using AMFPHP to connect Flash to an online mySQL Database.  I've written PHP class functions that query the database and return the query information to Flash. I take the query information returned and set the DataSet.dataProvider = to this query information.  One of the fields coming back from the database is a date field (string) in the format 'YYYY-MM-DD'.  I would like this field to be displayed in a DataGrid component that I have bound to my DataSet component in the format 'MM/DD/YYYY'.  It seems to me that the DataSet encoder and Dataset formatter would allow me to do this translation.  Unfortunately, I have tried every permutation I can think of and I still can't get the encoder or formatter to translate the date into the right format.  Does anyone know how to use the encoder or formatters on the DataSet?