How to change row/column header value?

<Grid.Resources>
           <conv:StringConverter x:Key="stringConv"/>
           <Style x:Key="colStyle" TargetType="{x:Type olapgrid:OlapGridTemplateCell}">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type 
                                  olapgrid:OlapGridTemplateCell}">
                            <TextBlock   Margin="5" Text="{Binding Path=CellValue,   
                                   Converter={StaticResource stringConv}}" Foreground="White"
                                   TextWrapping="Wrap" HorizontalAlignment="Center"
                                   VerticalAlignment="Center" FontFamily="Calibri" FontSize="12"/>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
</Grid.Resources>
<olapgrid:OlapGrid Name="olapGrid1" Grid.Column="0"
                       HorizontalAlignment="Stretch" VerticalAlignment="Stretch"   
                        ShowHeaderCellsToolTip="True" VisualStyle="Blend"
                        OlapDataManager="{Binding GridDataManager}">
                   <olapgrid:OlapGrid.SummaryRowStyle>
                        <olapgrid:OlapGridCellStyle Style="{StaticResource colStyle}"/>
                   </olapgrid:OlapGrid.SummaryRowStyle>
</olapgrid:OlapGrid>

public class StringConverter : IValueConverter 
    {
       public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
       {
           string val = "Enter the text you want to display";
           if (value != null)
           {
               if (value.Equals("Total"))
               {
                   return val;  
               }
           }
           return value;    
       }
    }

Public Class StringConverter
                  Implements IValueConverter
                  Public Function Convert(ByVal value As Object, ByVal targetType As Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object
                                   Dim val As String = "Enter the text you want to display"
                                   If value IsNot Nothing Then
                                                   If value.Equals("Total") Then
                                                                   Return val
                                                   End If
                                   End If
                                   Return value
                   End Function
End Class