[otrs] Patching OTRS (LDAP Company)

I have a problem with my Active Directory configuration, the users' groups only appear in their distinguishedName attribute. I want to patch OTRS so that I can use the distinguishedName for the CustomerID value, however I want to use a substring inside the user's distinguishedName. For example the DN for a user is: CN=(name),OU=(group),DC=(...),DC=(...) I want to grab the "OU" section from that string. I'm wondering where I would make such a patch inside OTRS..? I can't seem to find where I would do this. I know perl so really I am just looking for the location of where this attribute gets retrieved/set. Thanks..! Greg