Copy the code in the light blue box into a new module and save it with
whatever name you like.

In the "on click" event insert the following:

On Error GoTo Err_txtDocs_DblClick
Dim strFilter As String
Dim lngFlags As Long
Dim DocPath As String

   strFilter = ahtAddFilterItem(strFilter, "All Files (*.*)", "*.*")
   'MsgBox "You selected: " &
    DocPath = ahtCommonFileOpenSave(InitialDir:="C:\", _
       Filter:=strFilter, FilterIndex:=3, Flags:=lngFlags, _
       DialogTitle:="Select Document")
   
   If Not DocPath = "" Then
       Me.AttDoc = DocPath
   End If
Exit_txtDocs_DblClick:
   Exit Sub

Err_txtDocs_DblClick:
   MsgBox Err.Description
   Resume Exit_txtDocs_DblClick

Create a text box called "AttDoc" (mine is bound) and whatever file you
choose will go into the field.

It does for me anyway.

What you do is copy everything between Code Start and Code End into a new
module (make sure it's not a class module nor the module associated with a
form. Also make sure when you save it that the name of the module isn't the
same as any of the functions or subs within the module)

Now, in the Click event of your button, put code similar to the 4 lines of
code at the top of the page.