using a macro to input a macro

Im looking for a way to input this macro into This_Workbook module of certain workbooks that I open.

Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
       Worksheets("Sheet1").Range("E1").Value = Now()
End Sub

I wish to add this code to certain workbooks without typing it inside of "This_Workbook" all the time, it needs to be in the workbook so that I can pass the workbook onto people and the date will update each time someone else saves the document too.

unless there is an easier way to do this?