Move that edge Toward by 95 % :
Do the same move for the other edge on the other surface.
You should end up with that :
Select these 4 vertices :
and make them the reference point of the move for the 'Move Toward ...' script.
Select the edge of the cube and move it toward by 50 %.
You should end up with that :
(beware of the 6 sided surface).
HTH.