Animation nodes - compare location vector at time

Maybe that’s not the right question. I’m trying to figure out an efficient way to figure out the distance an object has moved, ideally since the last AN trigger, rather than frame. But I’ll take frame if I have to do it based on time.
I thought I had it working at first, but then I realized the viewer for a list shows 3 decimals, while the location vector shows 4. And it’s doing math on the difference. So the length there was meaningless.

I’m moving an object around, and I just need to calculate the distance between now, and where it was before, so I can drive a wheel that is rolling all about. Of course, this method won’t work in reverse, but I think I have that figured out? By having another target that will always be in line with it, I can use the length of that to determine if the length should be positive or negative.

I just can’t figure out how to how to get the position of where the object was in the previous frame. The only thought I had, which is not ideal, was to use a particle emitter at 1 particle per frame (I’m still annoyed that you can’t set a particle emission rate rather than setting how many Total particles) and have a second object use the particle position. But that seems more complicated than it needs to be, if it’s even possible.