Define width of GridViewColumn by parent window

<GridView ColumnHeaderContainerStyle="{StaticResource CustomHeaderStyle}">

      <GridViewColumn Header="Available Roles"

         Width="{Binding Path=ActualWidth, RelativeSource={RelativeSource FindAncestor, cestorType={x:Type local:ListViewEx}}, Converter={StaticResource gridViewWidthConverter}, ConverterParameter=0.9}">