draw a box on your model that describes the outer limits of the drawing to use to reference the outer limit in CAM.
you may need to make the box just large enough to allow the tool to clear the top edges but not quite large enough to allow the tool to fit down twixt the box and the model edges.

there is likely a way of instructing your CAM package to do this in a simpler way but i do not know your cam package so you may have to "wing" it with a bit of trail and error.