binding "Mark Unseen" to a key

How do I bind Key-U to mark the current msg unseen?

I just upgraded (from 2.5.)  Msg_MarkUnseen has gone away.  I used
to have...

 set bindings(key,Msg_MarkUnseen) <Key-U>

...but now that doesn't work.

Using...

 set {bindings(key,Seq_Add $exmh(folder) unseen $msg(id))} <Key-U>

comes close, but the "scan" line in folder listing listbox doesn't
change to the c_useen color (blue.)

steve 
- - - 
systems & network manager
high energy physics
university of wisconsin