I wnated to write a simple formula like "=SUM(C12:C18)" in to a cell using VBA.

I have following code

Sheets(wsDestination).Cells(I, eColumn).Formula = "=SUM(C12:C18)"

The problme is I have the code in a for loop and I need change the cells
depends on the for loop index like

when I = 1 then "=SUM(C12:F12)"
when I = 2 then "=SUM(C13:F13)"
when I = 3 then "=SUM(C14:F14)"

The C and F depend on a variable to control.

Any information is great appreciated,