Do not run build while other dependant build is running

Hi all,

I have the following use case: Build C depends on build B which depends on build A. Build C runs once a day (schedule triggering) or manually. Build A runs when an SVN commit is done. Because build A deploys the artifact to a remote server and build C runs tests against it I want to set up a block of build A when build B or C is running. So is there any settings where I can block a "parent" build when any of its dependencies (on any level) is running?

Thanks

Tamas