It is possible to use the Dual MC33926 Motor Driver Carrier with an Arduino controller to drive a stepper motor; however, the code Jeremy posted above will not work directly since it is intended for the Dual MC33926 Motor Driver Shield for Arduino, which has additional circuitry to control it with DIR/PWM signals. You can see the extra components used by comparing the schematic diagrams on each board's product page. One solution might be to add that circuity to your setup so it functions like the shield.
Alternatively, you could modify the code to use the appropriate control signals. This would involve changing the way the
setSpeeds() command works in the library or changing the
setSpeeds() commands in each case of the switch statement to the equivalent commands for the Dual MC33926 Motor Driver Carrier.