Simple WPF Animation

Since I want to be able to visually demonstrate solutions to the sliding-block puzzle, I wanted a way to animate the WPF display. Below is part of the solution I've come up with. I don't know a huge amount about WPF, so this may look pretty off the wall and grim to experienced WPF-ers. If so, leave a comment and I'll try to make corrections.

(Presented “as-is” and without warranty or implied fitness; use at your own risk.)

First, the timer code:

type Animator () =

  let timer = 
    new System.Windows.Threading.DispatcherTimer()
    
  let stop () = 
    if timer.IsEnabled then timer.Stop()
    
  let animate (fCallback:unit->bool) 
              e =
    if not(fCallback()) then stop()
    
  member this.Start (fCallback:unit->bool)
                    (interval:int) =
    stop()
    timer.Tick.Add (animate fCallback)
    timer.Interval <- new System.TimeSpan(0,0,0,0,interval)
    timer.Start()
        
  member this.Stop () =
    stop()

And a simple use that makes random moves (to be placed within MainWindow or whatever class displays the Fifteen puzzle):

  let Animate  =
    let animator = new Animator()
    let rand = new Random()
    (fun interval ->
      animator.Start 
        (fun () ->
          moveTile(rand.Next 4)
          true)
        interval)