Traditionally, the way to extend Windows Search has been via IFilters (http://en.wikipedia.org/wiki/IFilters) that allow Windows to understand new types of files. This approach will certainly tie you into the Start button results.
In this case, you are dealing with federated search (http://msdn.microsoft.com/en-us/library/dd742958(VS.85).aspx), which makes online content act as if it were present on the user's computer.
Unfortunately, I can't find anything that obviously solves your problem. Consequently, you may have to build a kludge in 2 parts:
- An IFilter for your search results (say, a "*.C9" file).
- A file ending in "C9".
Incidentally, if you do a web search on the term "IFilter" and go to the first few search results, you might think that IFilters are no longer used due to a note at the top of the page.
If that happens, then you're at the old IFilter site. The current URL for the MSDN docs about this topic is at http://msdn.microsoft.com/en-us/library/bb266451(v=VS.85).aspx.
One last note of warning:
In Windows 7 and later, filters written in managed code are explicitly blocked. Filters MUST be written in native code due to potential CLR versioning issues with the process that multiple add-ins run in.