SQL数据库数据需换算导入chart图该怎么做

[zhangwenbin8]

Tablename = "POP2100" ;
string sql = string.Format("select * from " + Tablename + " where DATE='{0}' and MCHID='{1}' and TIME >='{2}' and TIME<='{3}'", GoDate, LiuhuaNo, startTime, endTime);
try
{
SqlDataAdapter sqldap = new SqlDataAdapter(sql, con);
DataSet ds = new DataSet();
sqldap.Fill(ds);
chart1.DataSource = ds.Tables[0];
chart1.Series["TEMP"].XValueMember = "TIME";
chart1.Series["TEMP"].YValueMembers = "TEMPOUT";
chart1.Series["PRESS"].XValueMember = "TIME";
chart1.Series["PRESS"].YValueMembers = "PRESSOUT";

chart1.DataBind();
}
catch (Exception ee)
{

ErrtextBox.Text = ee.Message.ToString();
}

}
数据库载入的数据TIME、TEMPOUT、PRESSOUT，，假如需要经过运算换算后载入chart图，，要怎么做？
chart1.Series["PRESS"].YValueMembers = "PRESSOUT";