Tex. Civil Practice and Remedies Code § 37.011: SUPPLEMENTAL RELIEF.

Further relief based on a declaratory judgment or decree may be granted whenever necessary or proper. The application must be by petition to a court having jurisdiction to grant the relief. If the application is deemed sufficient, the court shall, on reasonable notice, require any adverse party whose rights have been adjudicated by the declaratory judgment or decree to show cause why further relief should not be granted forthwith.

Acts 1985, 69th Leg., ch. 959, Sec. 1, eff. Sept. 1, 1985.