04Renault Kangoo, the center air vent 'flapper' that stops the air has stopped working.

We have an 2004 plate Renault Kangoo, the center air vent 'flapper' that stops the air has stopped working. i.e the unable to stop the air from comming out.
Looking at it I can see the control bar has broken off, how do I replace this.
I can see no way to get at it without taking the whole dash off.

thanks
John