The recommended way to do this would be to prevent developers from checking in these sorts of modifications to the .bld file, and instead use a GUI front-end to choose the dynamic build options and launch the build, passing macros on the command-line to specify which sections get built.
http://www.kinook.com/VisBuildPro/Ma...odelsample.htm
http://www.kinook.com/VisBuildPro/Ma...omptsample.htm
Another option would be to programmatically check the steps at the start of the build (in case the .bld file was checked in with steps unchecked) using the object model.
http://www.kinook.com/VisBuildPro/Ma...bjectmodel.htm
http://www.kinook.com/VisBuildPro/Ma...edproperty.htm
http://www.kinook.com/VisBuildPro/Ma...riptsample.htm