try
=if(Abs(A1)+Abs(B1)=Abs(A1+B1),Abs(A1-B1),if(A1<B1,-1,1)*Abs(A1+B1))

where your first number is is A1 and the second in B1

"Alistair" wrote:

I want to use Excel to evaluate the results of a psychometric test.
The test produces pairs of figures.
Each figure can be positive or negative

If both are positive or both are negative I want the absolute difference

If one is positive and the other negative I want to sum them
If the first is positive and the second negative then I want to maket he
figure produced above positive
If the first is negative and the second positive I want to make the figure
produced above negtive

Any ideas?