date sort

Hi everyone,
i need an urgent help. When i was sorting teh date column teh sorting wasnt functioning properly the sorting was happening on basis of day(my date format is dd/mmm/yyyy). so i was using the following code----
var myText = function(i, j){return myData[i][j]};
var myValue = function(i, j){return Date.parse(myData[i][j])};
obj.setDataProperty("text", myText);
obj.setDataProperty("value", myValue);
But the use of this restricted the sorting only to date column it isnt sorting other columns.
CAN ANY1 PLEASE HELP