Making textures that work with Macromedia Fireworks.

The title says it all. I have Macromedia fireworks, and acess to photoshop CS (it's not on my maschine though) so I'd like some advice on how to make a texture with transparancies in Fireworks, and what 'specs' the file needs, as in how to set an alpha channel, and suck. So far it looks like FW will open but not create a .tgs file and .jpeg doesn't support transparancies. Not sure about .tiff. Any advice would be helpful. Can't build avs without textures.

As far as I know TGA is the only format with alpha channel that SL supports. If Fireworks can't export TGA, you can't use Fireworks for creating textures with alpha channel for SL.