The program RC is freeware, and the writer is Diomidis Spinellis. I used it as a titling machine of my MDR 303. Therefor I wrote the script RC.MD6. I tried to program the 'A' key as ' a ', but there were timing problems. If you think you have a better script, I like to receive your version.
All alphabetical characters work, also do the numbers.
In that case, you can use the rotary control for that character. Left and right arrow are used to move within the character string. This will do it.