I'm not exactly understand what you are referring but if you want to something disappear when the marker is not shown you have do something like this:
Code:
import viz
viz.go()
#Add ARToolkit extension
ar = viz.add('artoolkit.dle')
#Create camera using first available webcam
camera = ar.addWebCamera()
#Create matrix marker
marker = camera.addMatrixMarker(0,width=1000)
#Add avatar model and set state 1
avatar = viz.add('vcc_male.cfg')
avatar.state(1)
#Link avatar model to marker sensor
viz.link(marker,avatar)
#Method that update if the marker is visible
def updateVisible():
if marker.getVisible():
avatar.visible(viz.ON)
else:
avatar.visible(viz.OFF)
vizact.ontimer(0,updateVisible)
I hope is that what you need