Key binding to '?'
===

I'm trying to add a keybinding onto a wpf datagrid when the user enters a '?' and have tried the following:

    <DataGrid.InputBindings>
                <KeyBinding Command="{Binding Path=OpenPrompt}" CommandParameter="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=DataGrid}, Path=CurrentCell}" Key="OemBackslash" Modifiers="Shift"/>
    </DataGrid.InputBindings>

i've also tried having the key set to 'Backslash' and 'Divide'.

Does anyone know how to do this?