Question: I want to set "Formula" to all cells in certain column **whatever the number of rows was**.

**But i don't want to set this function to first cell "Header" of this column**.

How do i make it ?.

Answer: 
I think you may have to reword this a little for people to understand exactly what you are after.
Are you trying to reference the range of all cells in a column except for the header? Most likely you can do this using an OFFSET with a COUNTA function inside, for example to get all of column A without the header you could use:

```
=OFFSET($A$1,1,0,COUNTA(A:A),1)

```

This assumes all the other cells in A have something in up to the end of the data range, no blanks in between.

What function are you trying to point at this range?
for example if you want to apply SIN(x) on a set of data in a row, in a vacant cell type:
=SIN("click on the first cell of the row")
then press "enter"
then grab the handle of this cell and draw it up to the last cell.
now you have a set of data in a row each cell of which is has the value of the SIN(the original cell)