how can unload movie texture from RAM

hello ; i have a lot video in my project i load this videos with class .how can i put a button to remove video from RAM because i have at least 30 video and when i play, video size goes to RAM and stay there when i play 10 video my RAM is completely full ! what do you think ? what do you think?

Call Resources.UnloadUnusedAssets , it will remove your dowloaded bytes from cache/Ram