Parallel development with binary files

Dealing with parallel development requires sometime to manage binary files or similar (eg. images, .mdb, .xls, .ppt) where the merge function cannot be applied.
To avoid conflicts, it is required to avoid parallel changes on those files, and let developers work only on a singolar version or stream, or at least alert users when a files is changed, or again create something like a reserved checkout.

Any idea on how to manage this situation with RTC ?
Is it possible to create locking mechanisms on those files (using extentions) ?

Thanks