use mousewheel change slice

[EnriqueBet]

Hi! I am trying to override the mouse wheel events of the QVTKRenderWindow and use it instead to navigate through my slices. Does anyone have any idea how to do that? I tried defining mouseUp and mouseSown functions to access to vtkImageReslice and vtkInteractorStyleImage and change the slice. But it just don't seem to work, maybe I am doing some rookie mistake. Here are my functitons:

 def MouseUp(obj,ev):
            if ev == "MouseWheelForwardEvent":
                    self.axialR.Update()
                    print("moving up")
                    matrix = self.axialR.GetResliceAxes()
                    slice = self.axialS.GetCurrentImageNumber()
                    slice += 1
                    self.axialS.SetCurrentImageNumber(slice)
                    self.axialR.Update()
                    self.axialW.GetRenderWindow().Render()

 def MouseDown(obj,ev):
            if ev == "MouseWheelForwardEvent":
                    self.axialR.Update()
                    print("moving up")
                    matrix = self.axialR.GetResliceAxes()
                    slice = self.axialS.GetCurrentImageNumber()
                    slice -= 1
                    self.axialS.SetCurrentImageNumber(slice)
                    self.axialR.Update()
                    self.axialW.GetRenderWindow().Render()

self.axialS.AddObserver('MouseWheelForwardEvent',MouseUp)
self.axialS.AddObserver('MouseWheelBackwardEvent',MouseDown)

where,

self.axialR = vtk.vtkImageReslice()
self.axialS = vtk.vtkInteractorImageStyle()

I will appreciate any help. Thanks in advance