A system for determining an intra-day net asset value proxy of an actively managed exchanged traded fund and the like includes a trusted computer system that has a physical hardware and operating system configuration in which domain configuration and trust relationships are established to determine access to information in the trusted system. The system also decrypts a file having adjusted portfolio information to provide security positions and calculates the intra-day net asset value proxy for the fund by applying prices received from a quote feed to security positions in the fund portfolio.