[Serusers] Prefix from the To user to the from user

Hi all This is my first post to the list, so I hope I can get some help. Here is the scenario. I'm building a SER server 0.9.6 with the following characteristics. I'll be supporting different companies with multiple locations each. The phone number will be 7 digits. First 2 digits are the company, the following 2 digits are the branch or location and the last 3 digits are the user number. So, let's say companyA digits are 21, and companyB digits are 22. CompanyA has two branches 10 and 11. Branch 10 has a user 100 (full number in subscriber table is 2110100), and a user 101 (full number in subscriber table is 2110101) Branch 11 has a user 100 (full number in subscriber table is 2111100). CompanyB has a branch 10 and user within the branch 100 (full number in subscriber table is 2210100) I want user when dialing within the same branch to be able to dial the other user number only. User 2110100 can dial 100 to reach User 2110101. But if he wants to dial User 2111100 (Same company different branch) he can dial 11100. And if he wants to dial a user within another company he has to dial the full 7 digits. No to SER config If ser receives a 3 digits number in the $ruri, it should extract the first 4 digits from the From URI and prefix the $ruri/username with them. If ser receives a 5 digits number in the $ruri, it should extract the first 2 digits from the From URI and prefix the $ruri/username with them. My problem is how to extract the first 2 or first 4 digits from the from URI. Any ideas? Thanks in advanced for your help, I have spent 5 days now trying to figure this one out. Ibrahim Hamouda