Making A Control "disappear" Behind Another Transparent One?

The "This is a test......" text is a label, that is the child of a Canvas. The Canvas is the child of the horizontal StackPanel that also has the blue Canvas with the team records on it as well as the team logo images and the team name labels. The black line is where the Canvas that holds the "This is a test....." label starts.I wan't the "This is a test....." text to roll from right to left, but the problem is that because all the controls on the StackPanel are transparent, the text doesn't "dissappear" underneath them, even when they leave the area of their parent control. How can I make them do that? ZIndex isn't the answer because my problem is not which control is on top, but instead the fact that the controls "above" it are transparent.