Need help with many-to-many relationships

Being new to Rails, I would appreciate some help defining some database
table relationships. I have the following tables:

waypoints
    id
    name

routes
    id
    name

routepoints
    route_id
    waypoint_id
    seqno

This leads to the Rails associations:

waypoints
  has_and_belongs_to_many :routes, :join_table => "routepoints"

routes
  has_and_belongs_to_many :waypoints, :join_table => "routepoints"

My problem is that routepoints defines an ordered list of waypoints for
a given route (using "seqno"). Is it possible to use acts_as_list
somehow? I will also need other attributes of routepoints (like
estimated time enroute, fuel burn, etc.).

Any ideas appreciated!

Thanks, Josh. Exactly what I needed...

--Eric