What I have implemented is simple, and we must bear in mind that the plugin in blender 2.5 is called for each frame of animation.
Initially exported normally, once exported, is called octane and begins to export the next frame and adding the frame number to the filename. When octane has finished rendering, the image is collected and added to the animation.
The process is repeated again with the next frame, but as it was exported in the previous step, instead of exporting it again, when detected that the file already exists with the frame number on the filename, this is renamed to the usual name and call octane. The process is repeated, exporting the next frame while rendering.
Cheers