It tends to be difficult to deal with alphanumeric grammars within IVR applications. To get around this limitation we had split up the grammars. This code assumes that the last 2 numbers within the jcode were actual digits. There is one issue with separating the grammars in this fashion. The grammars require a pause between entering the first portion of the input and the second. To make sure the users correctly input the jcode, you may want to prompt them to enter the first portion followed by a pause and then the second portion.
We have an undocumented IVR grammar entitled alphanum. We can't guarantee that this would be best for your application but we hope that it will help. The alphanum grammar works only with voice commands and to limit the amount of mistakes that may occur while using it we've modified the confidence and sensitivity levels. The alphanum grammar also adds in spaces between each entry, for example, 9 2 3 6 5 7 8 A P.