How do I pick the last tile changed on a tile map?

Title kind of says it all but I have a tile map that changes tiles to represent where sprites have been placed on another layer. Kind of like a mini map but thats not how I'm using it.

How do you think I could pick the last tile changed so if a sprite moved I could have a tile change and the previous tile/sprite location would revert to show it had moved?

Whenever you change the tile, record the x and y tile position in variables.