Data Validation: Uniique values based on two cells

[Saighead]

Hi,

Could you help me with a case-sensitive formula that would prevent duplicate values based on two cells? Now I'm using this for column C:
=SUMPRODUCT((--EXACT($C$1:$C$100000,C1)))<2

I need the same kind of thing, only it should evaluate column B as well. So, for example,

Column B　　　　　　　　　Column C
CEO　　　　　　　　　　　　　 John Doe
engineer　　　　　　　　　　 John Doe
programmer　　　　　　　　John Doe

should be evaluated as unique values.

Thanks in advance.

Also posted here.

 

[Eric W]

Perhaps:

=SUMPRODUCT((--EXACT($B$1:$B$100000&$C$1:$C$100000,B1&C1)))<2