Create two slate brushes with the relevant texture.
Slate brushes are created by right clicking on the content browser>User interfaces>Slate brushes. Then you just add the play texture in one slate brush and the stop texture in the other slate brush.w
Then do the following:
The make style node was created by dragging the in style pins and searching for make style node while the stop and play variables where created by dragging out the normal pins from the make style node and promoting them to variables and then setting the default value to the relevant brushes.