Comparing independent variables in a regression

I have performed a multiple regression (in SPSS). This is fine, and I've got significant coefficients which tell me their influence on the dependent variable. What I would like to be able to say is whether or not the effect that these independents have is different from each other.

Say that my independents are (with their Betas):

A 0.31
B 0.68
C 0.01

I'd like to be able to make the claim (or not) that A and B are different in their effect (all other variables being equal) on the dependent.

Thanks very much