Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)

    Dim i As Long, sht, shtsArr
    
    '   only one cell ?
    If Target.CountLarge > 1 Then Exit Sub
    '   within chosen range ?
    If Intersect(Target, Sh.Range("C2:C20")) Is Nothing Then Exit Sub
    '   which sheets ?
    shtsArr = Array("Sheet1", "Sheet2", "Sheet3", "Sheet4", "Sheet5", "Sheet6")
    '   is this a sheet in shtsArr ?
    For Each sht In shtsArr
        '   if so
        If Sh.Name = sht Then
            '   disable events
            Application.EnableEvents = False
            '   write to each sheets in shtsArr
            For i = 0 To UBound(shtsArr)
                Sheets(shtsArr(i)).Range(Target.Address) = Target.Value
            Next i
            '   re-enable events
            Application.EnableEvents = True
            '   no need to check further once found
            Exit For
        End If
    Next sht

End Sub