To attempt a Wizardly dispel, nominate a single Wizard in your army that is within 'Dispel range' of the Wizard that cast the spell. Dispel range varies depending upon the Level of the Wizard nominated:
Level 1 and Level 2 Wizards have a Dispel range of 18".
Level 3 and Level 4 Wizards have a Dispel range of 24".
Wizards that are engaged in combat, that are fleeing or that are not on the battlefield cannot be nominated.