<Grid xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
		 Margin="2" IsSharedSizeScope="True">

		<Grid.ColumnDefinitions>
			<ColumnDefinition  Width="Auto" SharedSizeGroup="myGroup"/>
			<ColumnDefinition />
			<ColumnDefinition SharedSizeGroup="myGroup"/>
		</Grid.ColumnDefinitions>
		<Button  Grid.Column="0"  Content="1"/>
		<Button  Grid.Column="1"  Content="2"/>
		<Button  Grid.Column="2"  Content="3"/>
		<GridSplitter  
                  Grid.Column="0" 
                  Width="5" Background="Red" ></GridSplitter>
	</Grid>