Splitting up archives

Is there any way I can configure Mhonarc to use part of a months archives?

I've just converted last months Majordomo archive which consisted of over 
700 postings an it becomes unwieldy tryin to access such a parge index 
file. 

Are there any recommended ways of restricting an index to a specific 
number of postings and then putting the remainder in another index?

-- 
John