i successfully did it. and it worked in batch render (i only tested from starting outside of maya). i create a very simple thing like: Code: expression -s "print \"test\\n\";" -o locator1 -n "runEveryFrame" -ae 1 -uc all ; and it printed the "test" in batch render before each frame. it was just the default - add expression to anything in the locator1 and name it "run every frame" with "run always" checked. worked like a charm. maybe you must not start it from within maya ???