Animation based on current transform and not presets

Okay, assuming this is a fairly basic question but I can't seem to solve it myself.

Say I have an anim moving a box from 0 on the x axis to -1 on that same axis.

If I was to trigger that animation 3 times, I'd like it to move my box from 0 to -1, then from -1 to -2 and finally from -2 to -3 instead of 0 to -1, then 0 to -1 again and 0 to -1 one more time. Does that make any sense?