I used an invisible button for this, by first putting a simple graphic symbol in place. Set up a simple gray square, 25 by 25 pixels, go to Insert>New Symbol and select Button. Edit the button, putting the gray square graphic symbol in the Up action. Go to Properties>Color Effect on the square symbol.  Set the Alpha effect to 0%, and you’re done. Right-click on the button on frame 1, choose Properties and click on the Actions tab. You need to set up a condition to stipulate that the timeline will jump to frame 2 and the flower animation should begin when the mouse moves over the button. The mouse cursor rolling off the button should bring the animation to a halt.