IF/ELSE formula with OR/AND issue

Hi Folks,
I have uploaded the question on an Excel 2010 file.
I always have trouble with this type of formula.

Here's what I am trying to do.
In column B, I have a sequence of letters A,B,C,D,E,F,G,H etc

In column E, I have the same letters A,B,C,D,E,F,G,H etc but in reverse or in no particular order.

I do not want to sort or filter anything. I want to write a formula like I have tried to explain on the Excel file.
I do not know how to incorporate the OR and AND parts of the formula correctly
Any help is much appreciated
Thank you