Hi,

You can find few very useful articles in our Desingers Guide. The part that you have to customize is AddNewRowSelectorCellControl. You then have to set the new Style to xamGrid.AddNewRowSettings.RowSelectorStyle.

The best way to attach a custom behaviour when the cell is clicked is to create a custom command. You can use the snippet below as a starting point:

public class MyCustomRowCommand : RowCommandBase
{
    protected override void ExecuteCommand(Row row)
    {
        MessageBox.Show("Clicked");
    }
}

public class MyCustomCommandSource : CommandSource
{

    protected override System.Windows.Input.ICommand ResolveCommand()
    {
        return new MyCustomRowCommand();
    }
}

...
<LinearGradientBrush x:Key="HeaderCellGlyphBrush"
                     StartPoint="0,0"
                     EndPoint="0,1">
    <LinearGradientBrush.GradientStops>
        <GradientStopCollection>
            <GradientStop Offset="0"
                          Color="#FFa3aeb9" />
            <GradientStop Offset="0.37"
                          Color="#FF8399a9" />
            <GradientStop Offset="0.370"
                          Color="#FF718597" />
            <GradientStop Offset="1"
                          Color="#FF617583" />
        </GradientStopCollection>
    </LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<Style x:Key="Style1"
       TargetType="igPrim:AddNewRowSelectorCellControl">
    <Setter Property="Background"
            Value="Red" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="igPrim:AddNewRowSelectorCellControl">
                <Grid>
                    <Border x:Name="border"
                            IsHitTestVisible="False"
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}"
                            Background="{TemplateBinding Background}" />
                    <Grid>
                        <ig:Commanding.Commands>
                            <local:MyCustomCommandSource EventName="MouseLeftButtonDown"/>
                        </ig:Commanding.Commands>
                        <Path Fill="#ffffff"
                              Stretch="Fill"
                              Stroke="{StaticResource HeaderCellGlyphBrush}"
                              StrokeThickness="1"
                              Data="M3.5,0.5 L6.5,0.5 L6.5,3.5 L9.5,3.5 L9.5,6.5 L6.5,6.5 L6.5,9.5 L3.5,9.5 L3.5,6.5 L0.5,6.5 L0.5,3.5 L3.5,3.5 z"
                              Width="10"
                              Height="10" />
                    </Grid>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

...

<ig:XamGrid x:Name="XGrid"
            ItemsSource="{Binding Data}">
    <ig:XamGrid.AddNewRowSettings>
        <ig:AddNewRowSettings RowSelectorStyle="{StaticResource Style1}"
                                AllowAddNewRow="Top" />
    </ig:XamGrid.AddNewRowSettings>
...

Hope this helps