Default editor content?

[MoMan]

I'm trying to use a certain forum on my site for product reviews, and I'd like to have users include product ratings, etc., in their replies. I wanted to use the extra threadfields mod for this, but it only works when posting threads, and not replies. Adapting it for replies would take a lot of extra coding and modification. So instead, I thought I'd take an easier approach, and simply add some default content to the message editor after a user clicks "post reply", and also to the quick reply box.

Is there any way to do with via the template editor, using conditionals so the custom text only shows up in a certain forum?

Attached is a screenshot of what I hope to accomplish. Any help would be appreciated!