Photoshop question 'Slices'

[massahwahl]

I use photoshop for creating websites and I was curious if there was a way when using the slice tool to 'slice' a layer. Meaning instead of only slicing a box area, can I turn a layer of the image into its own slice? This way I could do mouse over effects that would reflect different areas of the actual image without being restricted to only square blocks of the image.

If it can be done, please explain how. Thanks!

 

[massahwahl]

Forgot to add I have Adobe Fireworks as well if there is a way to do it in that program.