Dynamic Values in Animation Clip

I've only just got into using the animation window and animation clips for moving things around. I preferred using iTween or coroutines to move the objects manually in code.

The only problem I've come across so far is that I cannot find out how to move an object from a specified position.

For example: I have an entrance and exit animation for each menu in my game. Some of these objects move while the user is on the screen. For my exit animation I need to animate from wherever it happens to be, to the position on the last keyframe in the animation. Currently it snaps to whatever the first keyframe specifies.

Hope that makes sense :)