I have a VBA solution that asks for your number to be added and what position your value is. Once you have set your rules you select the text you require to be modified.
It works for renumbering terminals (what I wrote it for) but I don't think its ideal for you. I can probably modify it to do what you want but lets see if somebody has a more ready solution. If all the prefixes ar 2 letters mine will probably be quite easy to modify but if the number of prefix letters is variable then it won't be. (thinks, or will it? If I just.........)