Sub Test()
Dim rngToChange As Range
Dim iMultiplier As String
Dim iDivisor As String
With Sheets("Sheet1")
  iMultiplier = .Range("A1").Value
  iDivisor = .Range("A2").Value
  .Range("A3").Value = iMultiplier & iDivisor
  Set rngToChange = .Range("B1:B" & .Cells(Rows.Count, "B").End(xlUp).Row)
  .Range("A3").Copy
  rngToChange.PasteSpecial _
  Paste:=xlAll, Operation:=xlMultiply, SkipBlanks:=False, Transpose:=False
  Application.CutCopyMode = False
End With
End Sub