This isn't as easy said as done.
Currently the only way to subclass the chat windows is to use an external library.
However before something like this can be done you need to answer a few questions.
- How do you determine if the message is read? Would the counter only start if the window was minimized or would it be classified as read if the window is in the foreground?
- What would happen if 2 messages are received 10 seconds apart, do you reset the timer? Add a second timer? Ignore all subsequent messages?