InstaUp2Date Output names

Hi. I've searched, but couldn't find anything related. Sorry if this is answered somewhere else. I'm using InstaUp2Date and would like to put a date into the output name. In my Catalog file, I tried to set "Output File Name = instadmg`date "+%Y%m%d"" so that my output would be instadmg20090526.dmg This, of course, doesn't work. Anyone have a solution? Thanks. Rusty