how to do an inverted loop? do ( i-- ) Not ( i++ )

Hi ppl, well I have a small doubt, I needed to create a "for" loop, but I wish it were reversed, how can I do it?

example:

for "y1"

y1=Array.Height => y1=Array.Height-5 == --y

Instead of "for" use "repeat 6 times" and instead of loopindex use:

Array.Height-loopindex

thx, this will help me a lot :D