MSBuild - how to build only those projects that have changed?

Using MSBuild (and potentially other software if required) is there a way to only build the projects that have actually changed since the previous build? I'd then like the build process to build any dependent projects for those that have changed. The general idea is to speed up a long slow build process that currently builds everything each time it is run.

Thanks for any help.

You may want to look into implementing a build server such as http://www.jetbrains.com/teamcity/ or CruiseControl.NET

You have very granular control over all aspects of your build, and both are free. (Depending on project/team size for teamcity)

With this, you could set up each project to just build whenever a check-in happens to a codefile within that project.