I have 4 columns that contain amounts which can be the same in all four
columns, they can be different and can also be blank. If they are the same,
I want the amount only once but if they are different, I want to sum only the
amounts that are different. Blank cells can be ignored.

A B C D
500.00 500.00 500.00 = this would return value
of 500.00
100.00 100.00 200.00 200.00 = this would return value of
300.00