Disable attachments in 1 forum but enable external attachments

[Hornstar]

How would I go about disabling attachments in 1 forum, and then in that forum instead of having the attachments uploaded, I would like members to just use an external upload site such as Rapidshare. but to make it easier for members to understand I'd like a field in the thread manager that says Download Link: (or something along those lines)

Thanks.

[ranz]

My guess is that you'd need to hack the Attachment side of vBulletin or look for a mod that already does something similar.