errr Sequence.h and eiface.h are the files... Sorry.
http://bs-linux.com/Sequence.h
http://bs-linux.com/eiface.h
http://bs-linux.com/metamod_1.17_diff
the patch command under linux will apply the differences to your current files, no idea how you do this under windows though
If you want pre-patched metamod files let me know...