I've created a custom build step in Visual Studio 2010 that produces multiple files by running a command-line tool. The step creates these files as it should when invoking a build, but on a clean, it only cleans the first file I listed as an output of the step in the "Outputs" field of the custom build step. I've separated individual files with a semicolon and also tried the multi-line editor for the field and put each file on a separate line (VS inserts the semicolons when closing the multi-line editor). In any case, it doesn't seem to be the format of the field that's the issue - whatever file is first gets cleaned, the rest don't.
From reading the documentation, it seems that you should be able to have multiple files listed as output so that the step can properly clean any artifacts it produces. Does anything special need to be done to clean multiple files or is this a bug?