Determination of bank angle from speed and heading change per time period

Anyone know of a formula for determing the current bank angle, given the
current velocity and rate of change in heading over a particular period of
time? I was thinking of adding an artificial horizon to program that I'm
working on and figured that by taking the current velocity as reported by
the GPS and the change in heading as reported by the last two
course-over-ground measurements from the GPS, I should be able to
determine a close approximation of the actual bank angle... Of course,
this assumes that the current winds are ignored in addition to assuming a
coordinated turn... The current system that I am using only gets updates
at 1 Hz which might be a bit low, but I'm thinking of getting the Garmin
18 5 Hz unit which should be sufficiently fast in its update rate...