def METHOD_NAME(self,event):
    if 'lastPos' in dir(self.ypiezo[0]):
        p = self.ypiezo[0].lastPos[self.ypiezo[1]-1]
    else:
        p = self.ypiezo[0].GetPos(self.ypiezo[1])
    self.ypiezo[0].MoveTo(self.ypiezo[1], p - self.focusIncrement, False, vel=10)