var spread = new GC.Spread.Sheets.Workbook($("#ss")[0]);
 var activeSheet = spread.getActiveSheet();
 activeSheet.setRowCount(4, GC.Spread.Sheets.SheetArea.colHeader);
$("#ss").click(function (e) {
     // 列ヘッダセル内で、マウスでクリックされたセルのインデックスを取得します。
    var offset = $("#ss").offset();
     var x = e.pageX - offset.left;
     var y = e.pageY - offset.top;
     var target =spread.getActiveSheet().hitTest(x, y);
     if(target &&
         target.rowViewportIndex === -1 &&
         (target.colViewportIndex === 0 || target.colViewportIndex === 1)){
         console.log("Row index of mouse-clicked column header cells: " + target.row);
         console.log("Column index of mouse-clicked column header cells: " + target.col);
     }
 });