You should be able to get a reference to the storyboard in your code file
and add the event handler from there...
private void Method()
Storyboard ST = this.FindResource("Timeline1") as Storyboard;
ST.Completed += new EventHandler(ST_Completed);
void ST_Completed(object sender, EventArgs e)
You will need to check the syntax, I dont have VS or Blend open at the
See how you go,