The execution of a power can be compelled only where the power is mandatory, or is a power in trust;231 that is, a power held in trust, without any discretion as to its exercise, and in which the donee has no beneficial interest, will be enforced in equity in conformity with the trust, although not executed by the donee of the power. Thus where there is a power given to trustees to sell property and apply the proceeds upon trusts, and the trustees die without executing the power, the court will order a sale, and compel the heirs to join in the conveyance.232 A court of equity will not execute or control a discretionary power.233