stopping ontimer

[durf]

My program runs on onkeydown() that are assigned to different def func:. When i switch from func A to func B. A is still running. The reason is I think is becuase of the ontimers that I have associated with it. So is there anyway to stop and ontimer? Any other suggestions to handle this problem?

 
def funcA():

  def calculate():
  #CODE  

  vizact.ontimer2(0,viz.FOREVER,calculate)
vizact.onkeydown('a',funcA)

def funcB():

  def speed():
  #CODE

  vizact.ontimer2(0,viz.FOREVER,speed)
vizact.onkeydown('b',funcB)