Excel 2007 : Formula that copies automatically

[gjergji]

Using a formula i want cell a1 to copy the number 10 all the way until there is a new number, so until cell a4 then the formula will cell a5 all the way down to cell a8
i want to do this http://www.contextures.com/xlDataEntry02.html but in excel 2010

cell
A1---10
A2
A3
A4
A5---20
A6
A7
A8
A9---65
A10
A11
A12