Redmine

Hi,
I would like to modify redmine to do this but have no idea where to start.
1. when some one create a new issue. We got an issue id (ex: #100). I would like to modify redmine scrips so that once that issue #100 is created, a folder name: 100 will also be created at a specific location, lets say \\mini\redmine\existed_issues\100

How can i do it?
Please give me some hints.

OS Ubuntu Linux
Redmine version 1.4
Ruby version 1.8
RubyGems version 1.8.24
Rails version 2.3.14

thanks a lot