(e) an order refusing to register a memorandum of agreement or registering the same or providing for the registration of the same subject to conditions: Provided that no appeal shall lie against any order unless a substantial question of law is involved in the appeal and, in the case of an order other than an order such as is referred to in clause (b), unless the amount in dispute in the appeal is not less than three hundred rupees: Provided, further, that no appeal shall lie in any case in which the parties have agreed to abide by the decision of the Commissioner, or in which the order of the Commissioner gives effect to an agreement come to by the parties: 2[ Provided further that no appeal by an employer under clause (a) shall lie unless the memorandum of appeal is accompanied by a certificate by the Commissioner to the effect that the appellant has deposited with him the amount payable under the order appealed against.]