Display value in formula instead of reference to cell

The code below inserts a formula into the given cell resulting in "=E18*$A$1" where "A1" = the cost of the customer, see attachment: Copy of Row Columns.xlsm

Is there a way to modify this section of the code only (see below) where the result of the cell will return "=E18*0.3"? Now obviously I can enter "0.3" into the macro but the value in A1 will always change with every invoice, so the code needs to be flexible.

For Each rcell In Range(Cells(18, lc - 1), Cells(lr - 1, lc - 1))
 rcell.FormulaR1C1 = "=RC[-2]*R1C1"
Next rcell

Thanks in advance