  For a connected cobordism S between two knots K1,K2 in S3, we establish an
inequality involving the number of local maxima, the genus of S, and the
torsion orders of Kht(K1),Kht(K2), where Kht denotes Lee's perturbation of
Khovanov homology. This shows that the torsion order gives a lower bound for
the band-unlinking number.
