Specifying alignment when positioning

[jed]

When using absolute positioning is there a way to specify that you mean relative to the top or bottom? For example I want "bar" to always be at the bottom of the screen but I don't know what resolution they are running at. What I'm doing below will only work if they happen to be running at the right resolution.
With ogre I could just go: vert_align bottom


<Window Type="DefaultGUISheet" Name="root">
<Window Type="DefaultGUISheet" Name="bar">
<Property Name="Position" Value="x:0 y:.8" />
<Property Name="Size" Value="w:1 h:.2" />
<Window Type="TaharezLook/StaticImage" Name="bar/background">
<Property Name="MetricsMode" Value="Absolute" />
<Property Name="Position" Value="x:0 y:0" />
<Property Name="Size" Value="w:600 h:68" />
<Property Name="Image" Value="set:MainScreen image:bar" />
<Property Name="FrameEnabled" Value="false" />
</Window>
</Window>
</Window>