onAfterCMove

fires after the column has been moved to a new position

void onAfterCMove(number cInd,number posInd);

cInd	number	the index of the moved column
posInd	number	the index of the new position

Available only in PRO Edition

mygrid.attachEvent("onAfterCMove", function(cInd,posInd){
    //your code here
});