Switch parrenting beetwen 2 layers

\\Create Slider on Layer
layer1 = XXXXX.position; // Replace XXXXX with a pickwhip from first parent layer
layer2 = XXXXX.position; // Replace XXXXX with a pickwhip from second parent layer
slider = effect("Slider Control")("Slider")/100; //Slider will move between 0 to 100
(layer1*slider)+(layer2*(1-slider));