WPF DataGrid: How to perform column binding using code behind?

This is the column in question:

<DataGridTextColumn
    Header=" Length "
    Width="Auto"
    Binding="{Binding Path=Length, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, StringFormat=0.00;;#}"
    ElementStyle="{StaticResource RightJustified}"
    x:Name="lengthColumn"></DataGridTextColumn>

The problem is that I need to bind that column to some other property (called Length48) at run time.

TIA.