Hopefully it should do what you need. I think that an easier way to select them in the Task UI would be nice. It would also help bring to light the fact that such a feature even exists.
I searched around a bit and found some references- looks like it will do the job. Might even be able to use it in the SW remote to save me some pages, but I have to think about that one a little.
Does Substitution work for numeric properties or only alphanumerics? I see some hints towards that in other posts, and when I try to assign one, it won't take it and changes the value to 0.