Is there any programmatic way of changing message recipients (specifically To:)?

[Chris Green]

The subject says it all really. :-)

Is there any way that mutt can change the To: header of a message?
This could be either on its way to 'compose' or on its way out from
'compose'.

Basically I want to automate changing To: when replying to certain
messages where To: (and probably some other headers) match a
particular expression.

-- 
Chris Green