If you're in a Pop network, create an attribute @pscale_prev, then in a pop wrangle:
f@pscale = max(f@pscale, f@pscale_prev);
f@pscale_prev = f@pscale;
Otherwise you can use a solver, with an attribute wrangle, Input_1 in first input, Prev_frame in second input, and do:
f@pscale = max(f@pscale, f@opinput1_pscale);