Custom Permalinks optional to the standard URLs

Hi custom URL work great for me but I want it more as an optional feature. So I want to keep my structure and make the custom optional. This works of course but custom permalinks plugin changes the overall title URL of the post. example:

http://www.xtgamer.de/2012/05/20/im-test-prototype-2/

I want to keep this and want a costum URL named http://www.xtgamer.de/prototype2. To achieve that, I must change the title form in the post at the designated form to prototype2 but the plugin automatically also changes the current permalink, that is now:

http://www.xtgamer.de/2012/05/20/prototype2/

I dont want that. Can you please help me? Maybe there is a different plugin that achieves what I want.

Thanks!!

http://wordpress.org/extend/plugins/custom-permalinks/