The simplified example this; picture a Venn diagram made from two elements, A and B, that overlap. If I mouse over (A AND (NOT B)) all of A lights up. If I mouse over (B AND (NO
Use IsMouseDirectlyOver property. It seems to be thing you need.
http://msdn.microsoft.com/en-us/library/system.windows.uielement.ismousedirectlyoverproperty.aspx