Slider expression to adjust X position of two keyframes

@Mylenium 

I found this expression that works for the midpoints but it doesn't have the easing I need. 
Is there a way to add easing that reflects a velocity in and out of 67,67? 

var sliderValue = thisComp.layer("Control").effect("Footage position")("Slider");
var startX = 960;
var endX = 960;

if (time >= key(1).time && time < key(2).time) {
    easeOut(time, key(1).time, key(2).time, startX, sliderValue);
} else if (time >= key(2).time && time < key(3).time) {
    sliderValue; // Maintain the slider value once it reaches the second keyframe
} else if (time >= key(3).time && time < key(4).time) {
    easeOut(time, key(3).time, key(4).time, sliderValue, startX);
} else {
    value[0];
}

easeOut(time, key(3).time, key(4).time, sliderValue, startX); } else { value[0]; }

@Mylenium  How would the transform effect allow people in premier to adjust the position or anchor point only in the position when it's in splitscreen mode?