var cellType = new GC.Spread.Sheets.CellTypes.Button();
cellType.buttonBackColor("#FFFF00");
cellType.text("this is a button");
activeSheet.getCell(0, 2).cellType(cellType);

var cellType = activeSheet.getCellType(0,2,GC.Spread.Sheets.SheetArea.viewport)
if (cellType instanceof GC.Spread.Sheets.CellTypes.Button) {
      alert("This is a ButtonCellType");
}