  We consider the minimal three-form ${\cal N}=1$ supergravity coupled to
nilpotent three-form chiral superfields. The supersymmetry breaking is sourced
by the three-forms of the chiral multiplets, while the value of the gravitino
mass is controlled by the three-form of the supergravity multiplet. The
three-forms can nucleate membranes which scan both the supersymmetry breaking
scale and the gravitino mass. The peculiar supergravity feature that the
cosmological constant is the sum of a positive contribution from the
supersymmetry breaking scale and a negative contribution from the gravitino
mass makes the cosmological constant jump. This can lead to a
phenomenologically allowed small value of the cosmological constant even though
the supersymmetry breaking scale and the gravitino mass are dynamically large.
