VB Storyboard Animation setting SetTargetProperty - Store App

I'm looking at some old VB code which is doing a storyboard in code behind. It uses 4 images cropped from a larger image to create an animation (no change in screen position).  I think that I am ok until I get to the SetTargetProperty. I get a dependency property cannot be converted to string error. If I just put in a string like "0", the sb.Begin crashes hard. 

  Imports Windows.UI.Xaml.Media.Animation
...
  Dim sprite_sheet_position As New TranslateTransform
....
  Dim sprite_anim = New DoubleAnimationUsingKeyFrames
...
  'finally, we need a storyboard to tie the animation to the transform   
  Dim sb As New Storyboard
  sb.RepeatBehavior = RepeatBehavior.Forever
  sb.Children.Add(sprite_anim)
  Storyboard.SetTarget(sprite_anim, sprite_sheet_position)
  Storyboard.SetTargetProperty( _
       sprite_anim, New PropertyPath(Windows.UI.Xaml.Media.TranslateTransform.XProperty))
  sb.Begin()