Changing the direction of simple dc motor using one or max two counters

Hello
I am new to Labview. I was trying to run a simple linear dc motor by generating pwm using NI 9401. I have been successful in that. Now I want to change the direction of the motor digitally in the same program. I have used the second counter as well but it is also driving the motor in forward direction. How can I reverse the direction. Please help
Thanks