Rapid prototyping is an effective way for requirement validation in the earliest stages of software development. Our previous work RM2PT can automatically generate software prototypes from requirements models to support incremental and rapid requirements validation. Moreover, it can automatically generate the input parameters for each system operation in the prototype during the validating process. Although the prototype provides a GUI to help validate the requirements, this process is still challenging and time-consuming for stakeholders to select the system operations they need effectively due to the lack of a complete view of the business process. This paper proposes a CASE tool named ValidGen, which can automatically generate the validation scripts to execute the prototype without human interactions. The validation scripts are generated from the extended requirements model of RM2PT with the BPMN model to specify the invoking process between use cases to conform to the business requirements. Thanks to the validation scripts, the stakeholder only needs to monitor the execution process without selecting the system operation and typing the input parameters. We adopted three case studies to evaluate the tool, and the results show that the tool only needs about 60% of the time cost of the requirements validation than the original. Overall, the results were satisfactory. The proposed tool can be further extended and applied for requirements validation in the software industry.