One of possibilities is add tracefield to Pc-dmis program, as example:
TRACEFIELD/NO_DISPLAY,LIMIT=15 ; Drawing rev. : 7
Then modify label, add to REV NUMBER field:
=tracefield(1)
(1) is number of tracefield. If you have only one tracefield in a program then should be 1, if you have 4 tracefields in a program and tracefield with revision is 3-th, then should be (3).
No, you can't change the templates without changing the templates. What's your problem with changing the label template - write permissions? Talk to your boss, if you can't do your job because of restrictions they need to be revised.