If you are using the groove feature, open the dialog box in the left column. Select the "strategy tab" and click the box marked "reverse cut" to reverse the direction. Also if you have more than one curve selected it will reverse them all. That is why I like to split some things up, so I can get it to do exactly what I want. If you have a bunch of grooves that are parallel to each other, create one groove feature to your liking. Then select and paste the feature below the one you just copied. After that just open each copy up and select the curve that you want associated with that. At this point you can keep some in one direction and reverse the others. It sounds like a lot to do but it's REALLY easy.