[syslog-ng] Macro expansion in program destination

Is it possible to use macro expansion in the program destination. I wanted to write something like destination mydest{ program("/some/path/to/filter/program -options >> /path/log.$S_DAY"));}; I was hoping that syslog-ng would not open this destination until the first message was ready for this destination. I was hoping that syslog-ng would open a new one when the $S_DAY changed, allowing me to have each day of logs processed by my program with outputs based on day. Does anyone know if macro expantion can be used on program destinations? If not, can someone explain what I am overlooking that makes this a bad thing? Thanks, -- Evan Rempel