Query to map parts of shapefiles

[Chip Taylor]

I apologize if the title is somewhat misleading.  What I am trying to do
should be pretty common but I have not found a solution.

Environment: 
  Mapserver 4.6 running under Apache on Windows (soon to be changed to IIS
on Windows)
  No database.  PostGIS or MySQL to be added later.
  Little experience with PHP, MapScript in learning process

Data:
  Shapefiles of US, states, counties (all polygons)

Desired result:
  1. User brings up map of US and sees outlines of states. (have that
working - no problem).
  2. User selects a state by clicking somewhere within the state polygon OR
enters state name in text box (user choice - either is valid option)
  3. MapServer redraws map with desired state as extents
  4. User selects county from state by clicking somewhere within the county
boundary polygon or enters county name in text box (user choice - either is
valid option)
  5. Mapserver redraws map with desired county as extents.
  6. All this should be accomplished using the same base mapfile defining
layers, etc.

Any help with 2-6 would be most helpful.  Thanks in advance.

Chip Taylor
Prepared Response, Inc.