I need assistance in performing transient simulation for pressure inside a truck brake chamber.

Geometry :
Please refer the schematic below for initial and final states of the system.
Ignore the bolts, springs etc. Moving part is the red coloured plate attached to the diaphragm

Undeformed:
http://i29.tinypic.com/2a8iwt1.jpg
Fully extended
http://i28.tinypic.com/2iw58vn.jpg

Input:
I have measured data of mass flow rate vs time (total time = 30secs)as input to the system. Say m_in vs t.

Moving boundary:
I have measured data of the pushrod extension (red colour) vs time. Call xb vs t (again 30secs).
All in all, I have m_in and xb values as sample points sampled at 2ms for 30secs.

Problem:
a) I need to know how to write an UDF for the mass flow rate input and the moving boundary data xb (the output).
With these two given, I need to solve for the Pressure developed inside the chamber as a function of time.

b) Max movement of xb is 2.25 inches. I need to have a dynamic mesh so that the flow domain is enlarged corresponding to the movement of the boundary at each time step.

c) Medium is compressed air.

kindly give suggestions for implementing a) and b)
Thanks for your time

Srivatsan