如何实现chart中每条条曲线读取excel表中不同位置 急~~

[Evilxxx]

现在的代码如下所述，在时间列和本次列下面我想第二条曲线读取从第5行开始 怎么设置啊 大神们


private void button1_Click(object sender, EventArgs e)
{
OpenFileDialog fileDialog = new OpenFileDialog();
fileDialog.Multiselect = true;
fileDialog.Title = "请选择文件";
fileDialog.Filter = "所有文件(*xls*)|*.xls*"; //设置要选择的文件的类型
if (fileDialog.ShowDialog() == DialogResult.OK)
{
string file = fileDialog.FileName;//返回文件的完整路径
}
chart1.DataSource = dt;
chart1.DataBind();
string a, b;
dataSet1 = ExcelToDataSet(fileDialog.FileName);//读取选取文件

foreach (DataRow dr in dataSet1.Tables[0].Rows)
{
a = dr["时间"].ToString();
b = dr["本次"].ToString();
if (a == "")
{
break;
}
if (b == "")
{
break;
}
chart1.Series[0].Points.AddXY(Convert.ToString(a), Convert.ToString(b));
chart1.Series[1].Points.AddXY(Convert.ToString(a), Convert.ToString(b));
}
}

static public DataSet ExcelToDataSet(string filename)
{
DataSet ds;
string strCon = "Provider=Microsoft.Jet.OLEDB.4.0;" +
"Extended Properties=Excel 8.0;" +
"data source=" + filename;
OleDbConnection myConn = new OleDbConnection(strCon);
string strCom = " SELECT * FROM [工程数据表$A3:J1000]";
myConn.Open();
OleDbDataAdapter myCommand = new OleDbDataAdapter(strCom, myConn);

ds = new DataSet();
myCommand.Fill(ds);
myConn.Close();
return ds;
}