I need the Expand / Collapse for RowDetailsTemplate

Question

I have wpfTolkit datagrid. He has DataGrid.RowDetailsTemplate I need to do the button when clicked it will Expand / Collapse.

How to do this I could not find the event you want

<Custom:DataGrid RowDetailsVisibilityMode="VisibleWhenSelected" SelectionMode="Extended" CanUserAddRows="False" CanUserDeleteRows="False" CanUserResizeRows="False" CanUserSortColumns="False">
    <Custom:DataGrid.RowDetailsTemplate>
        <DataTemplate>
            <Custom:DataGrid>
                <Custom:DataGrid.Columns>
                    <Custom:DataGridTextColumn Binding="{Binding idClient, Mode=Default}" Header="Ид" IsReadOnly="True"/>
                    <Custom:DataGridTextColumn Binding="{Binding name_client, Mode=Default}"  Header="Имя" IsReadOnly="True"/>
                </Custom:DataGrid.Columns>
            </Custom:DataGrid>
        </DataTemplate>
    </Custom:DataGrid.RowDetailsTemplate>
    <Custom:DataGrid.Columns>
        <Custom:DataGridTemplateColumn>
            <Custom:DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <Expander IsExpanded="True"/>
                </DataTemplate>
            </Custom:DataGridTemplateColumn.CellTemplate>
        </Custom:DataGridTemplateColumn>
        <Custom:DataGridTextColumn Binding="{Binding idPartner, Mode=Default}" Header="Ид" IsReadOnly="True"/>
        <Custom:DataGridTextColumn Binding="{Binding name_partner, Mode=Default}"  Header="Имя" IsReadOnly="True"/>
    </Custom:DataGrid.Columns>
</Custom:DataGrid>