Key framing motion to a motion tracked 2d image?

[RedSpectrumPictures]

I'll try and keep this as simple as possible, I am new to AE and am struggling to do the things that I want to.
I have motion tracked a 2d image to follow the Y axis of a video clip.
The 2d image now moves up and down in sync to the movement in the video
I now want to keyframe a horizontal movement to the 2d image, so it moves from left to right whilst keeping the Y axis motion track.
I have had no luck trying to do this, anyone help please?

 

[Michael Carter]

If you tracked your footage correctly, best-practices means you applied the track data to a null and parented that to the 2d element.

That leaves you free to animate the postion of the 2d element itself. You can animate position or anchor point to get what you want.

If you applied tracking data directly to the 2D object, animate whatever is free, position or anchor point.

Or you could render your y-motion layer with an alpha channel, drop the rendered footage back in, and add the other axis movement.