New to excel formulas and need help with a problem.

example:

A B
3324 jpr
2756 jpr
3324 jpr
2856 slt
3492 slt
5864 bdg
2856 slt
2756 jpr

I am trying to get a count of the jpr's in col B , that have a
different number in col A.
the solution in this example should be 2 for jpr.