how I can optimise this macro?

Here's the loop but I'm sure there's a better way:

Dim i As Long
For i = 1 To 15
Range("B" & i).FormulaR1C1 = "=SUM(Sheet1!C[" & 9 + i & "])"
Next

Regards

Or,

Range("B1:B15").FormulaR1C1 = "=SUM(INDEX(Sheet1!C12:C26,0,ROWS(R1:R)))"

@mithil - please retitle your thread to something more appropriate - "optimise code" or some thing along those lines