how can i setType for a dynamic columns ?

i'm using datatable, and i'm creating dynamically columns which are containing float data , so for sorting the data i should change the type of the column using this function : jQuery.extend( jQuery.fn.dataTableExt.oSort, { "formatted-num-pre": function ( a ) { a = (a==="-") ? 0 : a.replace( /[^\d-.]/g, "" ); return parseFloat( a ); }, "formatted-num-asc": function ( a, b ) { return a - b; }, "formatted-num-desc": function ( a, b ) { return b - a; } } ); and set the type like that :( this works for the static column) "aoColumns": [ { "sType": "formatted-num" }] how can i do it for columns dynamicaly created? thanks