You can do it with call manager route patterns.
Creat a route pattern for each code like this-
9.1xxxxxxxxxx if your code is 2222 then it will be 92222.1xxxxxxxxxx the end user will have to dial 922221xxxxxxxxxx.
point that at a route list. do not do any digit strip on the route pattern, but do a pre-dot digit strip on the route list. this will insure that the access code is inserted into cdr. If you digit strip on the route pattern, only the outgoing phone number is logged.
You can create a RP for each code, or generalize them with wildcards like this-
92xxx.1xxxxxxxxxx just make sure it won't overlap with any of your other RPs.
This is fairly easy to imeplement, and will track usage, unfortunately it will also show the access code in the placed calls directory on the phone, and it is fairly easy to guess the code, because CM will let you try as many combos as you want without locking it out.
