How do I only display a custom bbcode to logged in members?

[I.M.O.G.]

I want to create a bbcode that only displays its contents to registered members, similar to the way the code bbcode works on vbulletin.com/org

For example, this would be my bbcode: [registered]Only registered members can view whatever I type here[/registered]

This is what I figured out so far:

1. I found this post, which describes most of what is required to accomplish this:
https://vborg.vbsupport.ru/showpost....17&postcount=3

2. And I know this is the code to only display something to a logged in member:
<if condition="$bbuserinfo[userid]">$value</if>

Can someone help me put 1 and 2 together correctly? I am not sure how to create the function properly that I would need. Any help is appreciated.