$("#button1").click(function () {
     var spread = new GC.Spread.Sheets.Workbook(document.getElementById("ss"),{sheetCount:3});
     var sheet = spread.getActiveSheet();
     //最上行および最左列のインデックスを取得します。
    var topRow = sheet.getViewportTopRow(1);
     var leftCol = sheet.getViewportLeftColumn(1);
     alert("Index of top row being displayed: " + topRow + "\n" +
         "Index of first column being displayed: " + leftCol);
 });