Thanks Paul, sorry for not getting back earlier.
It's all about speed in rendering. What I want to do is simply render a preview file to quickly check a few things (like camera movement). And I don't need every frame to be in it. It is okay if the preview file just shows every 10th frame. Rendering every 10th frame makes the rendering 10 times faster. And that is what I want to achieve because I don't care if the output is choppy - it's a preview anyway.
I have found the "-i" option with aerender.exe:http://livedocs.adobe.com/en_US/AfterEf ... EC0B5.html
That is exactly what I need. But would be nice to have it in After Effect itself.
Thanks for any hints.