How to specify data with two fields, no delimiter, variable length?

[Roger L Costello]

Hi Folks,

I have a data field composed to two items. 

The values for the first item can be enumerated:

        A
        ABC
        AB
        AC

The values for the second item is any integer 0-999

So, here is a same data field:

        A250

How do I parse that using DFDL? I reckon I'm stuck.

/Roger