What's the trigger for your animation? Unfortunately I don't know the best "Blendable" way to accomplish this, but it should be easy enough to wire up in Xaml. You might end up with something like this:
<Button>
<Button.Triggers>
<EventTrigger RoutedEvent="Button.MouseEnter">
<BeginStoryboard>
<Storyboard>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</Button.Triggers>
</Button>
That should cause your storyboard to run when the mouse enters the button. I know that's not the same as the hover event that you were after, but I think you could add a delay to the animation to compensate for it. If that doesn't help could you post the Xaml you're working with?
This article discusses animation triggers in Xaml but it might have more a developer slant than you'd like:
http://msdn.microsoft.com/en-us/magazine/cc721608.aspx