Need Help with 5e Crit Macro!!

Hey guys, so I'm not even going to pretend that I understand macros in the least, or coding for that matter.  Even after trying to read the wiki and other posts on this forum, I still don't understand how macros work or how something like an attack macro makes things simpler than going to a character sheet and clicking on the weapon I'm attacking with.  I almost want someone to explain this to me like they would a child.  My question is, is there a way to embed text into a roll that only shows up if it is a 20?  For example, let's say we have a barbarian who has been using the same axe for awhile and finally they roll a critical hit.  But what's this? The axe has a special ability that only activates on a critical hit!  Basically, is that possible and what would that look like?  I would really appreciate the help.

It depends which character sheet you are using, but it may be possible to rig something up for you.

Just the OGL version

Are you wanting to be able to do this through the character sheet or through a custom macro?

Whatever is easiest. All of it goes right over my head

In a custom macro this would be extremely easy to do, simply put the desired text in the crit &nbsp;field of the dmg or atkdmg template.&nbsp; <a href="https://wiki.roll20.net/5e_OGL_Roll_Templates" rel="nofollow">https://wiki.roll20.net/5e_OGL_Roll_Templates</a> &amp;{template:atkdmg} {{mod=mod}} {{rname=rname}} {{r1=r1}} {{always=1}} {{r2=r2}} {{attack=1}} {{range=range}} {{damage=1}} {{dmg1flag=1}} {{dmg1=dmg1}} {{dmg1type=dmg1type}} {{dmg2flag=1}} {{dmg2=dmg2}} {{dmg2type=dmg2type}} {{crit1= CRIT TEXT GOES HERE }} {{crit2=crit2}} {{save=1}} {{saveattr=saveattr}} {{savedesc=savedesc}} {{savedc=savedc}} {{desc=desc}} {{hldmg=hldmg}} {{spelllevel=spelllevel}} ammo=ammo {{charname=charname}} For other values, set up the attack as normal in the character sheet, click the attack, then push the up-arrow key on your keyboard while typing something in the chat window. This will give you the exact code used for that attack.Then just manipulate the code as needed.