comparison of kappa coefficients

[Gerhard Rumpold]

Does anyone know about a method to compare two cohen-kappa values, if they
are significant different from each other.

I have a Kappa(t1) of r=.64
 and     Kappa(t2) of r=.72 .

How can I compute that at the time t2 the Kappa is a real improvment
compared to t1.

Thanks in advance
Gerhard Rumpold