A dropdown list in Word is less dynamic than a file open dialogue, since you would need to repopulate the list every time you access it to ensure it remains current. Also, adding more files to the list wouldn't add them to the folder. To populate and keep refreshed your content control with such a list you might use code like the following in your document's 'ThisDocument' code module:
Code:
Private Sub Document_ContentControlOnEnter(ByVal CCtrl As ContentControl)
Application.ScreenUpdating = False
Dim strFolder As String, strFile As String, strDocNm As String
strDocNm = ActiveDocument.FullName
strFolder = ActiveDocument.Path
strFile = Dir(strFolder & "\*.doc", vbNormal)
With CCtrl
.DropdownListEntries.Clear
.Type = wdContentControlText
.Range.Text = ""
.Type = wdContentControlDropdownList
While strFile <> ""
If strFolder & "\" & strFile <> strDocNm Then
.DropdownListEntries.Add strFile
End If
strFile = Dir()
Wend
End With
Application.ScreenUpdating = True
End Sub
The above code populates the content control with a list of documents in found in the same folder as the document containing your content control.
To retain the previous selection, omit:
Code:
.Type = wdContentControlText
.Range.Text = ""
.Type = wdContentControlDropdownList