That looks promising.
The big picture is whenever Country, Type, Speed or other fields that effect price change, call a function similar to ff_CselRegion_action that
- recalculates valid type and speed option, say validTypes and validSpeeds arrays.
- updates options array on type(speed) selectors per validTypes(speeds).
- if current type(speed) not in valid... set to 'none'.
- if have data on all fields needed to calculate price, calculate it.
- update element where price is displayed with calculated price or blank value.
The individual field action functions will then have little else to do.
Hope that helps