Nested Boolean logic

Hi,

I'm trying use advanced Boolean logic for report variables. I need to count widgets that have 1 characteristic less the combination of 2 characteristics. For instance I need to identify widgets with A but not B&C. So, in theory, if condition A is met and not(condition B and condition C) then 1 else 0.

I've written it as =if ([A]=1 and (not([B]=2) and not([C]=3));1;0. However it treats each condition equally so I'm not counting all the widgets I need to count.

Thanks for your assistance.