Alright, so I reckon this should be easy for one of you, but I just can't work it out.

Got a formula in one cell that references some other cells. I want to drag the formula down a load of rows, but I want the cell references in the formulae to go up by 9 in each row instead of 1. So, eg, I'll end up with:
=B1+C1
=B10+C10
=B19+C19
etc

Using Excel 2007, y'all. Happy Wednesday.