How to set the default application for ABD to use ABD MicroStation mode

All

I want to change the way a DGN file is opened on a PC that has ABD installed.  At the moment if I double click a dgn file within Windows Explorer, it opens with the full ABD version.  I want to change this to use the ABD MicroStation version.  As you are aware there is an icon for this, but via the DGN properties > Open With option, there isn't an option. I can select the ABD.exe file but I am unable to define the BB_Discipline.....  

Anyone know how to change this

Thank you 

Ian