I think irishqt wants to "forward" a portion of the actual chat to a person...not just forward one part of it. In bbm there is a way to copy the chat, but I don't think SMS is allowing this function. I wish it would let you copy what you wanted and paste it into the field. Because even with the copy chat in bbm, it copies the entirety of what is there. If you find out how to do it, could you please post back?
*Oh, and a while back, a friend and I found a work around that required mms and screen captures. Just took pictures of the screen, sent them, rinse, wash, repeat. Not the most efficient way, but it worked.