Redirect to external login

[adamle]

Greetings,

I want to change the url that a non logged in user is redirected to when trying to make a post. Right now they get redirected to the vBulletin login form, I need them to be redirected to a different link, my intergrated site login form, it logs then in to vBulletin too.

Anyone know which template, or hook needs to be altered for this?

Thanks in advance.
Adam.