Hi,

Right click the sheet tab, View code and paste this in. Change the range to
suit

Private Sub Worksheet_Change(ByVal Target As Range)
  If Target.Cells.Count > 1 Or IsEmpty(Target) Then Exit Sub
   If Not Intersect(Target, Range("A1:A10")) Is Nothing Then' change to suit
       If IsNumeric(Target) Then
           On Error Resume Next
               Application.EnableEvents = False
               Target = Target / 5.7
               Application.EnableEvents = True
           On Error GoTo 0
       End If
   End If
End Sub

Mike