Can someone tell me how to code this?

1. I'm in the first row of the last column,
2. I insert a column
3. I insert a formula into the first cell of the new column. (My
options are set so that I don't move the active cell when I hit
enter.)
3. With the active cell at the top of this new empty column, I do a
shift-ctrl-end to select a range that includes the first cell in the
new column, to the last cell in the spreadsheet.
--here is where the recorded macro breaks--
4. Still holding the shift key down, I left-arrow one column. So now
I have only the new empty column selected. This is the next to last
column in the spreadsheet.
5. Fill down the formula from the first row to the last row.

The recorded macro captures this code for the selection process:

Range(Selection, ActiveCell.SpecialCells(xlLastCell)).Select
Range("T1:T3107").Select

It seems that when I did the shift-left-arrow, it selected the
absolute range, "T1:T3107". So now if the spreadsheet I want to work
on has 3108 rows, my macro doesn't know that and effectively "breaks".

I've tried using the VBA help file, but can't seem to find out how to
make this code more generic. I'm thinking I need to do something
like a "ActiveCell.SpecialCells(xlLastCell)-1". I found the offset
command, but I don't seem to be able to use that here (or can't
figure out how!).