[ANNOUNCEMENT] Heroes 3: World Tournament - an add-on for tournament games.

Is it possible to implement a new spell in the spellbook (or modify one of the old, unnecessary ones) that would prevent creatures from flying? For example, a basic magic spell could make a flying creature travel half the distance by flying and the rest on foot, an advanced spell could prevent it from flying altogether, and an expert spell could be cast on all flying creatures, preventing them from flying.