[WriteLog] CW Message S/N Forms

[Joseph Young]

%3 in the CW message below produces numbers of the form
001, 002, etc. How do I change the message to produce numbers
of the form TT1, TT2, etc.?

%C %BQSO B4%B %3 %3 AZ AZ
 
I have found some informationin the  HELP file but not
"how to do it". Thanks and 73 de Joe, W6RLL.