Addition and scrolling

Hello!

In the past I have used a sheet that allows you to add data to a cell in the following manner (assuming the cell contains the number 5):
I could highlight the cell; press +5 and it would then display 10 while the formula bar would show something like =5+5.

1) I'm trying to do this now and it keeps replacing data instead of adding to it. How would I fix this?

2) Another, less important, question I have is; is it's possible to auto scroll to a column when you open a file (i.e. it's the 12th, so it scrolls to the 12th row)?

Thanks!

Edit: On a side note; I saw someone ask about inserting pictures. I have a graph I tried to "send to back" so it sits behind the data input cells.
3) It didn't work, so I guessed it wasn't possible; is that right?