This Script Driving Me Crazy :/

I’m (newbie)

and all what i want of mikrotik to do this small script that seems easy for u all

i want it to catch any user active or not ( in users list ) ←
and see if he is in profile named ( limited ) then if his limit is ( 0 )
set the limit to 20mb for examble thats it i dont request anything more

i tried million times to do it by myself and google it but found nothing :confused:

my Current OS is 5.2 :confused: hopefully u can help me with that . Thanks.