How can you set IsHitTestVisible to True on a child of something where it's set to false?

I have a message which is within a border and is displayed in front of a MDI client area. Because it's just a message, I set it's IsHitTestVisible to false. For convenience, I've also included a button within it so the user can simply click the button to start a new diagram.

However, because the border has its IsHitTestVisible set to False, it shorts out the True value of the button so the user can't click on the button.

That said, how can you make a control invisible to the mouse, while still allowing one of its children to receive mouse events?

Here's a screenshot:

We want the blue area with text to be hit-test invisible, but we want the button to still be able to be pressed. Thoughts? (And yes, I already know about stacking the two items in a grid, but that messes with the layout.

Ok, doesn't look like the question can be solved as asked, and therefore it looks like we have to revert to the layered method. In that case, to compensate for text changes, you have to set the vertical alignment of the button to Bottom, and ensure there's extra padding on the bottom edge of the border or bottom margin on the TextBlock) to ensure the label always floats above the button. You manage the side margins/padding for both using the same principles.

This will give us what we're after, but just seems pretty cumbersome. Again, I wish there was some way to specify IsHitTestVisible (or IsEnabled for that matter) with a 'Force' somehow that re-establishes them (and below) as the owner of the behaviors. A person can dream. Until then... layers it is!