iis 7.5 - IIS 7.5 URL Rewrite looping

I have a webapp that is located in /subdir1/subdir2/ I'd like to simplify it for the users by adding a subdomain sub.domain.com but it keeps looping. I'd tried to add additional rules to prevent it but no joy.

So what happens is http://sub.domain.com/subdir1/subdir2/subdir1/subdir2/subdir1/subdir2/subdir1/subdir2/subdir1/subdir2/subdir1/subdir2/

My rule in web.config:

Any ideas?

Edit:
So what i'm really trying to do is make it easier for the users. Right now they have to type www.domain.com/subdir1/subdir2/ to access the login page for the product. What I wanted to do was create a single subdomain that would rewrite to the above link. Rather than typing the long url just go to sub.domain.com and it would redirect or rewrite to the www.domain.com/subdir1/subdir2/ location. I hope that makes my desire a bit more clear.

Thanks!