SUMIF but ignore if duplicate in columns

[jsavoia]

I have a spreadsheet that looks like this:

A B C D
100 100 4.00 AR
100 4.00 AR


I need a formula that will Sum column C if column D is "AR" and if colulmn A is "100" but not to count it if "100" also appears in column B.

Help!

Thanks, JoAnn

 

[T. Valko]

Biff,
This formula is simply amazing. Seriously. Thank you.

You're welcome. Thanks for the feedback!

 

[Cheko]

This formula works for me but my workbook is to heavy to handle it, is there a way around this without array (slowest thing ever)? Also no pivot, no calculated list it has to be only formula.