How to update the source to the latest version before every build?

I have a project A with a dependency to project B.
A has subversion path http://host/RepoA/Trunk, revision 10
B has subversion path http://host/RepoB/Trunk, revision 50
Those are different subversion repositories.
Project A is only built if project B was successfully built.


If I commit a change into project A, which will create revision 11, project
B will be built before A, since there is this dependency.

If Project B still has revision 50, Project A will use revision 10(Because those were the revision
which were used for the last build).
In my case this is wrong. I want Project A to use the current revision(11 in this case)
in order to build the project.

Is it possible to set this behaviour in order to get always the latest source of a repository used?