Conditional Formatting, How to test for Length, and numbers and letters only?

[Joyner]

Hello, I can't figure this one out and can't find it posted anywhere.

I want to do conditional formatting on cells to test for cells that don't meet the criteria of six characters long, that can be a combinations of numbers and letters only. The cell can be only numbers, or only letters, or any combination of numbers and letters, but no special characters, etc.

How would I write the conditional formatting formula to test for that?

Thanks for any help.

 

[Joyner]

Upon further testing, yours works Andrew, and mine doesn't...Thanks