What do you mean 'calling' C1?

The formula is being put in column C from row 3 down.

I got R1C from this in the original code, but I missed the [].
ActiveCell.Offset(1, 0)
Try changing R1C to R[1]C[-1], which is one row down and one column to the left from the cell the formula is in.

PS You could just use B4 in the formula and change FormulaR1C1 to Formula.