Corrective Blend Shape Puzzle? Can you Solve?

Hey chaps,

I’m attempting a rig for the first time in blender, using rigify to start off with. One issue im having is with a corrective blend shape for the hips. The driver I’ve created for it (driven by x local rotation) activates in both directions of the leg movement? Is there a way to fix this so it only activates in a certain rotational direction? Can’t seem to find anyone else with this issue.

Thanks guys