[WriteLog] What exactly does %X do?

[Don Hill AA5AU]

I am set up for SO2R on one PC in RTTY mode which is completely new to me since I normally use two PCs networked.  What I am trying
to find out is if there is a command you can put into a message to force that particular message to go out on a particular radio.

The only thing I can find remotely resembling this is the %X command, but I can't figure out what exactly it does.  The HELP file
says:

"F2 through F11 move the transmit focus to match the keyboard focus before transmitting . You can change this behavior on a
message-by-message basis by adding a %X at the beginning of the message buffer, which retains the transmit radio focus."

What exactly does %X do?  And how is it used? 

73, Don AA5AU
http://www.aa5au.com
http://www.rttycontesting.com