How can I do this?

[oldlan]

I am new to vBulletin, and would like to seek help here.

Suppose I have a url in a message.

[url="http://www.site1.com"]

, and I would like vBulletin to display the following html code

<a href="http://www.site2.com/redirect.php?tid=xx&url=http://www.site1.com">

in stead of the default one

<a href="http://www.site1.com">

The

http://www.site2.com/redirect.php?tid=xx&url=

is automatically added when people browse this thread. Where the xx here is the thread id.

Please give me some clue on how to do this? At least let me know which file (funciton) I need to look at and do the modification.

Thanks a lot!