Another way to do this would be to do an Exclusive OR of the Button6 and Button7 values and feed the result into a case.
False would set the motor speed to zero.
True would feed the value of Button7 into and If, the true leg = +1, false leg = -1. Output of IF would be multiplied by .5 and fed to motor speed.
The Labview XOR looks like this:
XOR returns FALSE if both values are either TRUE or both values are FALSE, otherwise it returns TRUE.