grid = new dhtmlXGridObject('gridbox');
    
    grid.enableMarkedCells();
    ...
    grid.unmarkAll(); // set a whole grid as unmarked
    
    var markedArray = grid.getMarked(); /* the array of marked cells
                        (pairs of row id and column index)*/
    ...
    /* onCellMarked event occurs when cell is marked*/
    
    grid.attachEvent("onCellMarked",function(row_id,column_index){
        ...
    })
    
    /* onCellUnMarked event occurs when cell becomes unmarked*/
    
    grid.attachEvent("onCellUnMarked",function(row_id,column_index){
        ...
    })