Here is suggested language that your board can add to the house rules.
If a dispute arises out of or relates to [this proprietary lease or these bylaws] or the house rules, or the breach thereof, including any dispute between [unit-owners or shareholders], and if the dispute cannot be settled through negotiation, the parties shall attempt in good faith to settle the dispute my mediation before resorting to litigation. The mediation shall be conducted in New York City by the _________ under its _________ Rules or any successor organization or a panel or independent party selected by the Board that is satisfactory to each of the parties to the dispute. The mediation shall be conduced in accordance with the mediator's rules then in effect. The fees, costs, and expenses of the mediation will be borne equally by the disputants. This mediation clause shall the [assignment or termination of the proprietary lease or transfer of the unit].