Sorry I didn't reply earlier -- I just returned from an internet-free vacation with the family in Hawai'i. A great trip, but I missed the entire Garritan Go-Round sale! So so so so sad ... especially since I planned to order JABB when I returned, and just found out I missed a fantastic deal on it. Oh well ...
The difference between Hannes' post and mine (besides that fact that he is brief and I am long-winded) is that he addressed Dan's actual question of sending MIDI into Reaper. Dan said that he is already using Sibelius->MapleMIDI->CoMB, so Hannes' suggestion of using Silelius->MapleMIDI->Reaper->CoMB(VST) matches Dan's request better than my suggestion does.
However, I prefer to save the data from my Finale score as a MIDI file and load the file into Reaper, rather than sending the MIDI data into Reaper directly from Finale. I get three benefits from doing it this way:
1) I can edit the data using the Reaper MIDI editor, which I find easier to use than the Finale MIDI editor.
2) I get the same timing/tempo for each performance (Finale HumanPlayback introduces slight variations for each performance, which can sound bad if you are trying to sync to other tracks in Reaper).
3) I have more CPU available for Reaper, because Finale doesn't need to be running to play the file.I assumed that Dan might benefit by doing it my way, so I didn't think of using the method Hannes suggested. But if Dan is already successfully playing the music from Sibelius into CoMB through MapleMIDI, and doesn't have the other issues I brought up, then he may prefer Hannes' solution over mine.