How to deploy Macro

I have used Custom Fields in my DOCX file and update them using OpenXML, but custom fields are not getting updated in document.
So I have write following macro to update field, it run well on my machine, Now i want to deploy it on each machine at client side, the machine count is 500 I can not go on each machine and paste macro code in each normal.dot file
what is easy step to do it ? Or when I open word file, will application ask for installing macro ? like addin ?
How to do it please help

Here is my macro

Code:

---

Private Sub Document_Open()
  Dim aStory As Range
  Dim aField As Field
  For Each aStory In ActiveDocument.StoryRanges
      For Each aField In aStory.Fields
        aField.Update
      Next aField
  Next aStory
End Sub

---

Thanks in advanced for help

any code will only work for users with appropriate macro security level

Thanks for reply.
But what step do I need to follow to deploy macro on each machine ?

the normal method is to use an addin