Several studies using VR exposure therapy for PTSD have been conducted to date, with promising results. The need for better accuracy of the patient's arousal assessment requires aggregation of various measures of arousal, including physiological ones, which may increase the mental burden on the therapist. Assessment of the patient's arousal, automated by the computer, may therefore be useful. As the therapist also needs to manipulate user interface to introduce appropriate trigger stimuli in the virtual environment, automated adaptation of VR scenarios in response to the patient's level of arousal may alleviate this task. This paper describes the architecture of the software that performs appropriate automation according to the rules of graded exposure therapy, and discusses issues for successful implementation of such software.