Set formula to a range of cells
Range("C1:C10").Formula = "=A1+B1"
Simple as that.
It autofills (FillDown) the range with the formula.
I think this is the simplest answer possible: 2 lines and very comprehensible. It emulates the functionality of dragging a formula written in a cell across a range of cells.
Range("C1").Formula = "=A1+B1"Range("C1:C10").FillDown
I would update the formula in C1. Then copy the formula from C1 and paste it till C10...
Not sure about a more elegant solution
Range("C1").Formula = "=A1+B1"Range("C1").CopyRange("C1:C10").Pastespecial(XlPasteall)