Create post by script?

I’d like to integrate WP with videoDB. videoDB users shold be able to discuss movies. So: in videoDB, I’d like to show ‘Discuss…’ link which goes into WP and, either searches for an already existing post of this movie or creates a new one, adds the movie id as custom field and let’s the user write the text (generic guest user).

Any idea if/how this can be achieved?

Thanks,
Andi