external links target=_blank, internal links target=_top?

[boatdesign]

The default behavior in vBulletin is that when someone posts a URL vBulletin converts it to a clickable link and adds target=_blank. This is great for when people post links to other websites, etc. so that my forum stays open in the background.

But when people post internal links to other threads, it can get annoying for them to open in a new window.

Is there any way I could create an "if else" logic that would:
-add target="_blank" when creating autolinks to any external url
-except add target="_top" when creating autolinks to mydomain.com/forum threads?

(I guess the if else logic would actually work the other way around, if the URL=myurl, vBulletin would add target="_top", else it would add "target="_blank".

How would I do this exactly?