In this paper, a Customizable and Dynamic Locking (CDL) scheme is proposed for concurrency control in Internet-based real-time collaborative editors. The idea of dynamic-locking is that: locking mechanism dynamically determines locking set according to locking policies and latest collaborative activities happened in the shared workspace, and pre-locks objects for succeeding editing and preventing from other user's edit. Dynamic locking is optional: user decides whether and when to use locking mechanism. In the proposed scheme, locking policy is separated from locking mechanism. Locking policies can be customized for different collaboration tasks. Locking scope is dynamically determined according to locking policies and collaborative activities among users. Multiple users can select different policies in the same collaborative session, and change locking policies at different phases of collaboration as well. Protocols and algorithms for locking conflict resolution and consistency maintenance are also presented in this paper.