bbcode syntax: if either opening or closing tag is not correct format, then reject

[timetunnel]

Hello.

How to write the syntax for the following:

"if EITHER opening OR closing bbcode tag is not in the correct format, then reject"

I have the 'standard' pattern I need for each tag; I'm just not sure which syntax / steps to use to create this condition.

I've already created the error to halt the save if either tag is not typed correctly, I just need a way to catch the incorrectly-typed tag.

Thanks in advance.