Without knowing the design of your project, it is hard say which solution might be the best fit. You might want to look at the On Application Start interaction if your slideshow can be triggered as the project is first running. Another solution might be to trigger an Action Sequence. This might work if there is a starting event, and you do not need it to loop.
There are some solutions that use other parts of the Flash Platform. You could build the slideshow in Flash Professional and bring the swf into Flash Catalyst. Or you could use Flash Builder to add some ActionScript to programmatically do your slideshow.
I know this doesn't give you a direct solution, but hopefully some initial pointers for you to explore.