if(tb.rows.length>2)
    {
        var row = tb.rows.length;
        alert(row);
        //如果只有一条数据
         if(row == 3)
             {
                 if(document.all.SPBM.value=="00")
                 {
                     //alert(document.all.SPBM.value);
                     alert("请录入发票信息");
                 }
             }
        //如果不止一条数据
        if(row>3)
        {
            for(i=0;i<row-2;i++)
             {
            if(tb.rows[i+1].cells[0].children.item(0).value=="00")；
             {
               alert("请选择品名!");
                return false;
             }
          }
        }
    }