[NTG-context] highlighting aligned formulas

Hello, Is it possible (using ConTeXt MKII) to put a frame (and/or other highlighters) around an aligned multiline formula, and also around a single line of this equation array? (The equation number should align correctly outside the frame.) \mframed within an alignment seems to refuse the job. Digging the mailinglist brought up a 2006 hint of Hans referring to a \definealigned command which I also could not bring into action. Thanks, Andreas ps Asking as a new user it may be naive, but I still didn't figure out how to uncomment multiple lines (for debugging).