Using GetCursorPositionRAS and ignore a model

I am using GetCursorPositionRAS on the vtkMRMLCrosshairNode singleton to get my mouse position when I am hitting a certain model. This works perfect.
But now I would like to continuously display a stylus when hitting it. (with a certain colour, transparency, radius etc). For this I created a separate modelNode (sphere) and displayed it at the hit location.

But when the stylus is placed the next mouse hit will be the stylus itself. Can I ignore a certain model from the CrosshairNode? or should I display a stylus in another way?

You can call node.SetSelectable(False) to exclude node from picking.