Jay :

This may help you.

To do his you need it :
The Member ID of your co-worker
The Message ID Thread

Then :

1-Create a new message and chose the second tab from new message screen (create a new…)
2-Type the Member ID of your coworker in the Textbox at the right of the screen.
3-In the message area type MESSAGE#1019120 (here 1019120 is the Message thread ID). With some comments of you.

Bye