Inertia script (I think)

Hi,

Can anyone help…?

I’m try to do a ghosting type thing where a box moves across the screen then back again.
The thing is I’m after a sort of ghosting following it as it moves which is affected by its speed ie the faster it goes the ghosting becomes stretched etc.

I think it’s going to be some sort of scripting concerning inertia maybe a single slither of faded box that multiplies itself?

Anyone have any ideas?

Thanks

Spence