column length

[wildcat4545]

I see where there is an option to set column length min and max. 
But my needs are just a bit different.
I only want it to accept a length of 18 or 33.
Nothing more, and nothing less.

Iv tried this:
(OR(LEN(columnName1) = 18, LEN(columnName1) = 33), "Valid", "Invalid") 

and, no matter what i input, it says invalid.
And also, i dont know if this will go in app formula field, or data validity>"valid if" field.

[dbaum · Accepted solution]

To Check form input validity (Valid_If) - AppSheet Help use an expression that returns true if the input is valid. For example:

OR(LEN([[_THIS]) = 18, LEN([_THIS]) = 33)

[wildcat4545]

you are a lifesaver @dbaum 
had to tweek , (delete extra bracket) but You got me there
OR(LEN([column1]) = 18, LEN([column1]) = 33)
I put in the validity field, works perfect.
I feel like iv been messing with this for daaays.
Thank you thank you!