protected void GridView1_RowDataBound(Object sender, GridViewRowEventArgs e)
{
    const int ColumnName = 2;
    //now you can use this const as column name
    if (e.Row.RowType == DataControlRowType.DataRow)
    {                
           e.Row.Cells[ColumnName].Text="data";        
    }  
}

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
 {
 if (e.Row.RowType == DataControlRowType.DataRow)
 {
 	string strVal = ((DataRowView)e.Row.DataItem)["YOUR_COLUMN_NAME"].ToString();
}

 void CustomersGridView_RowDataBound(Object sender, GridViewRowEventArgs e)
  {

    if(e.Row.RowType == DataControlRowType.DataRow)
    {     
      label lbl = (label) e.Row.FindControl("lblHidden");
      DropDownList ddl = (label) e.Row.FindControl("ddlID");
      
      if(lbl.Text =="A")
      {
        ddl.Items.Clear();
        ddl.Items.Add("B");
	ddl.Items.Add("C")
      }
    Else if(lbl.Text =="B")
      {
        ddl.Items.Clear();       
	ddl.Items.Add("C")
      }       
    }

  }