Rules on/mechanics for a fight 'round a moving carriage

[TheKemarden]

So I have an idea for a module-sized adventure revolving around a haunted carriage. While developing the concept, I realized that I have no idea how to make this work mechanically in a table-top format.

The idea is that the PCs are chasing down the vehicle, jump onto it, and enter it's larger-than-it-appears-on-the-outside interior. Any suggestions for making this work in the Pathfinder rule system?

[Echobeats]

Can't you just move the carriage a set number of squares each round, at the top of the initiative count? Ideally a number less than the PCs' speed. Have a separate battle grid for inside if there is going to be simultaneous action there.

I'm not entirely sure what you see the problem as being. Have I missed something?

[TheKemarden]

Oh, right, that would work, wouldn't it?

[LunaLovecraft]

If you need to, assume the ship rules. If a unit can't keep up, they move backwards on the board. Update the terrain as necessary, maybe cut out some basic props if you want trees and stuff to be a factor.