I have a set of structure macros on the related section of my website. A 16-bit FOR...NEXT is included. The front page of the section is at
http://wilsonminesco.com/StructureMacros/ . I don't have it for the Kowalski assembler, but if someone adapts it (or does something similar, even if it's not an exact match to my structure macros) for Kowalski's, I'd like to link to it, or even host it if you don't have a place to put it. (Actually, for that matter, they could also go here on 6502.org though.) See also the links at the end of that page, and elsewhere on that page. I have a couple of more-extended examples of the usage starting about 70% of the way down my "Simple Multitasking" page at
http://wilsonminesco.com/multitask/index.html .