var comment = new GC.Spread.Sheets.Comments.Comment();
comment.text("new comment!");
comment.backColor("orange");
comment.displayMode(GC.Spread.Sheets.Comments.DisplayMode.alwaysShown);
activeSheet.getCell(5,5).comment(comment);

activeSheet.bind(GC.Spread.Sheets.Events.CommentRemoved, function (e, info) {    
       console.log("sheet name: " + info.sheetName);
});
