SiteWide RSS import

Hello,

I’ve got a WordPress3 MultiSite installation.
The WWW (main site) is a kind of “portal”, linking to the others.

I’m trying to set up a script which imports content from several external RSS feeds. I’d like to write ONE script which imports the content in several blogs (subdomains) of my installation.

I know how to retreive the information from the feed, how to format it (into an array), and how to use wp_insert_post to insert a post. But when I do so, the post is in the main site.

Is there an easy way to post to another blog of the installation ?
I’m thinking about some kind of parameter passed to wp_insert_post, or some config to override. Do you guys have any leads?

Thank you very much, I hope I’ve been understandable.