I'm trying to formulate:

If it's mixed case, copy it. If it's all lower case or ALL CAPS, then make it PROPER.

ie, if 'bananas' is in A1 and B2 says =PROPER(A2), then B2 says Bananas, because PROPER capitalises the first letter of each word.

I would like to do 
=if(or(A1=ALL UPPER CASE,A1=all lower case),PROPER(A1),A1)
How do I do?