How to create three state expander in C# WPF?

How to create Three State Expander in C# WPF? Using Two expanders, Need to have Three state for both, minimize, restore and Maximize. When restoring both expanders should occupy equal height. When maximizing, one has to minimize and other has to maximize and occupy full area. How to achieve this?

<pre><Grid DockPanel.Dock="Top" Name="myExpanderGrid">
                        <Grid.RowDefinitions>
                            <RowDefinition>
                                <RowDefinition.Style>
                                    <Style TargetType="RowDefinition">
                                        <Setter Property="Height" Value="auto" />
                                        <Style.Triggers>
                                            <DataTrigger Binding="{Binding IsBottomExpanded}" Value="True">
                                                <Setter Property="Height" Value="*" />
                                            </DataTrigger>
                                            <DataTrigger Binding="{Binding IsBottomExpanded}" Value="False">
                                                <Setter Property="Height" Value="5*" />
                                            </DataTrigger>
                                        </Style.Triggers>
                                    </Style>
                                </RowDefinition.Style>
                            </RowDefinition>
                            <RowDefinition>