When dragging a formula, how to make it go opposite direction?

Hi Guys,

I need to have my formula move opposite direction.
For example, if in Cell A2, I have "=A1*2", and normally, if I drag the cell down, Cell A3 will have "=A2*2", but that's not what I need. I need it to be B2*2 (So the formula refers vertical not horizontal).

Is there a way to do that?

Thank you!
Jolene

PS. Sorry about the typo for the title... didn't realize it till I post it