I have this code:

Private Sub Worksheet_Change(ByVal Target As Range)
Const WS_Range As String = "b9:c9"
Dim iColumn As Integer
Application.EnableEvents = False
Application.ScreenUpdating = False
On Error Resume Next
    If Not Intersect(Target, Me.Range(WS_Range)) Is Nothing Then
        iColumn = Target.Column
        If iColumn = 3 Then
            Range("b9").Value = Range("c9").Value / Range("b13").Value
        Else: Range("c9").Value = Range("b9").Value * Range("b13").Value
            End If
        End If
Application.EnableEvents = True
Application.ScreenUpdating = True
On Error GoTo 0
End Sub
It is a simple dynamic conversion tool. Whereas in Excel, we usually have one input cell and one output cell. Through this code, both input cells are also output cells. I.E. Converting Dollar to Peso or Peso to Dollar, Meter to Inches or Inches to Meter....

Problem is, this code only specifies two specific cells, namely b9 and c9 with b13 as the conversion factor. How can I expand the code to include multiple pairs of cells. I.E. A1:B1, C10:C11,etc by 1) Using the same 'conversion factor' cell (b13) and 2) Using different conversion factors located in different cells on the worksheet.

Many thanks,

lex