Shape key driven between 2 axis

I have a question of shape key expression.
so now i have a Object it have 5 shape key

*E is for fixing when
So i have create a Bone to driven all the shape key:
+Y = A
-Y = B
+X = C
-X = D

then now i want if the bone move between +Y and -X the D shape key will increase the value. but if i only move +Y or -X will not affect any of shape key E,and I have tried made shapekey E driven by +y and -x 50%, but the problem is if i just only use +Y shapekey E will increase 0.5 (becasue 50% driven).i dont know what can i do for it, can anyone help? thanks


*** Moderation ***
moved from: Lighting and Rendering
*** End of Moderation ***

It’s easy to have multiple inputs for a driver.

You just need to use two input variables (click “add a variable”).
One variable reads the y position, one reads the x.

Unfortunately Blender doesn’t offer many unscripted ways of combining these values, but if you sum them together (in the “type” dropdown menu), I think that will work the way you need it. Apparently you can manipulate the two inputs however you like with python scripting, but I don’t know how.

Hope that helps!