Real-time collaborative programming supports a team of programmers to concurrently edit a shared set of source code at the same time. To support semantic conflict prevention in real-time collaboration, prior work had proposed a dependency-based automatic locking (DAL) approach, which grants locks on selected source code regions based on a set of prefixed rules. To further improve the flexibility of the DAL scheme by utilizing programmers’ knowledge on semantic conflict risks and collaboration requirements, we propose a novel Request-Invitation-Approval (RIA) scheme, which allows any programmer to manually request the editing permission on a locked code region, or invite another programmer to share locks on a region. To support the proposed scheme, we have further proposed two modes for the permission transfer process, and contributed detailed techniques on four request patterns. Prototype system implementation has validated the feasibility of the approach and techniques, and user evaluations have demonstrated the satisfactory usability of the system.