How can I get and set contents of a particular cell in Flex DataGrid? e.g. myDG.Cells(col,row) should return me contents of Cell at [col] Column

How can I get and set contents of a particular cell in Flex DataGrid? e.g. myDG.Cells(col,row) should return me contents of Cell at [col] Column.
I have some function
private function updateCells():void {
....
.....
}
In my Flex DataGrid I have 7 columns out of which 4 has been binded with dataFields but rest of the 3 need some calculation done on the basis of those 4 columns.
I call updateCells function on creationComplete event of the myDG (My DataGrid).

Any help would be appreciated. Thanks a ton in advance.