CreateUserWizardControl - how to exit and display error

Hi

I have a CreateUserWizard control which is highly customised

On this void:

 protected void CreateUserWizard1_CreatingUser(object sender, LoginCancelEventArgs e)
    {

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I want to call another void called checkAuthorisedEmployeeNumber

    void checkAuthorisedEmployeeNumber(string EmpNo) { 
    
        if (EmpNo == "123456"){
            //user not allowed to register
            //exit the create user wizard and show error message
            
        }

    }

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This is working, but i want to cancel the createUser process and show an error message saying that the user isn't in the authorised list, and cannot register

Can someone help with this code please