<p>I'm trying to create a pimped-out version of the slider that has a user control in the "thumb"-part (meaning: the moving thingy on the slider) that reacts to the slider's movements. Basically my current demo / development version is just a UserControl with 5 visual states that just make it change a smiley face to an angry face in 5 phases. I'd like to put that user control into the thumb.</p>

<p>My only problem is as follows: I can get the UserControl into the thumb no problem, by editing the Slider-control's template in Expression Blend. However, once the UserControl is in the ControlTemplate, it's no longer visible to the new user control class and thus is not changeable with VisualStateManager.</p>

<p>So basically, my question is two-fold:</p>

<ol>
<li><p>Is there any better way to replace the thumb of the Slider-control than editing it's template?</p></li>
<li><p>If not, how can I access stuff I've added to the template?</p></li>
</ol>

<p>Thanks for any answers! </p>

I'm answering myself. After visiting every single page on the internet, I finally figured out a solution by myself!
I added a Loaded-event handler to my control in the ControlTemplate and in that event handler I took the reference to that control for the actual class! After that I was able to refer to that control with that reference and for example visualstate changes worked like a charm!
I've now got a hopped-up slider that has a smiley in the handle part and the face on the smiley changes in relation to the position of the slider! Pretty cool!