Setting "Worked" field in a comment or reply via email

Hello,

When I add a comment or reply via the web interface, I can set the
"Worked: __ minutes" field. Is there a straightforward way to set
this field via an email comment or reply? If not, how hard would it
be to hack this in, and where would I start?

Paul.

w http://logicsquad.net/
h http://paul.hoadley.name/