I think you'll have much better luck using Illustrator or Photoshop for this type of warped text effect.
That said, Fireworks' Path panel does offer a few commands that allow you to use a path to influence the contour of other paths beneath it. For example, here are some quick and clumsy attempts at using an ellipse to modify text—first with Fisheye Paths and then Deform to Path. Before applying these commands, the text must be converted to paths using Text > Convert to Paths.
...Not really the effect you're aiming for, obviously. You could also try to create the desired effect by hand, first converting the text to paths, and then using the Subselection tool (and keyboard arrow keys) to select and move points individually.
Here are some additional links on this topic:
It looks like Aaron Beall, the developer of the Path panel, went so far as to create an "Arc Bottom" command that could be used to distort text in the shape of an arc. However, I don't see one for distorting text along the top.
hi, thanks for the advice, i'm checking out the links now