WPF DataGrid full row multi selection style

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WPF

DataGrid

I'm stumbled on this ridiculous problem for a few days now, and would appreciate any bits of wisdom any one has on the matter.
I'm trying to implement a DataGrid with multiple row selection that will set the last selected row (focused row if i may, tho it appears to not be supported by the DataGrid object) to have a different background from the other selected rows and draw a border around it.
I need a virtualizing control, so a ListView is not a viable solution as far as i know.
How would one go about it in WPF? I managed so far only disable the cell selection rectangle...
Thanks in advance!

Edit: In order to further clarify what i'm trying to do i post my latest failed attemp..:

<DataGrid.RowStyle>
    <Style TargetType="{x:Type DataGridRow}">
        <Style.Triggers>
            <MultiTrigger>
                <MultiTrigger.Conditions>
                    <Condition Property="IsSelected" Value="True"/>
                    <Condition Property="IsFocused" Value="True"/>
                </MultiTrigger.Conditions>
                <Setter Property="Background" Value="#FF3399FF"/>                            
                <Setter Property="BorderThickness" Value="1"/>
                <Setter Property="BorderBrush" Value="Black"/>                            
            </MultiTrigger>
            <MultiTrigger>
                <MultiTrigger.Conditions>
                    <Condition Property="IsSelected" Value="True"/>
                    <Condition Property="IsFocused" Value="False"/>
                </MultiTrigger.Conditions>
                <Setter Property="Background" Value="#993399FF"/>
            </MultiTrigger>
        </Style.Triggers>
    </Style>
</DataGrid.RowStyle>

This would work nice if only the row will somehow get focus....
I do wonder why is the IsFocused property even there if DataGridRow don't receive focus?