Cell Mapping using the mouse

[semo]

I am trying to work out how if you scroll you mouse over a cell or Cells it maps the data to cell A 1

ie If the mouse scrolls over C1,D1 and E1 it highlight them and what ever is in D1 is mapped to A1 and so forth. I have seen it done but the guy wont help out.



. A B C D E
1 X . 1 1 16
2 .. . 2 17 32
3 .. . 3 33 48