use Firebird SavePoints to implement a Undo/Redo system in Delphi

I need somebody to show me how I can implement a Undo/Redo system in Delphi. I use Delphi 5, FB v. 1.5 and IBObjects v. 4.7 . The coder will provide a working testing application with a TDBGrid, Undo and Redo buttons. If I apply changes to the grid and push the UNDO button, the previous containt of the grid should be shown. The Redo would be nice, but I am afraid it cannot be easily done, so this is an optional requirement.