Try:
Sub SplitDoc()
Application.ScreenUpdating = False
Dim Rng As Range, DocSrc As Document, DocTgt As Document, StrNm As String
Dim Ext As String, FlPth As String, Tmplt As String, Fmt As Long
Set DocSrc = ActiveDocument
With DocSrc
Ext = "." & Split(.Name, ".")(UBound(Split(.Name, ".")))
FlPth = .Path & ""
Tmplt = .AttachedTemplate.FullName
Fmt = .SaveFormat
With .Range
.InsertAfter vbCr & "///"
With .Find
.ClearFormatting
.Replacement.ClearFormatting
.Text = "[//]{3}*^13"
.Replacement.Text = ""
.Forward = True
.Wrap = wdFindStop
.Format = False
.MatchWildcards = True
.Execute
End With
Do While .Find.Found
If .End = DocSrc.Range.End Then GoTo Finished
Set Rng = .Duplicate
With Rng
.MoveEndUntil "///", wdForward
StrNm = Split(Split(.Paragraphs.First.Range.Text, vbCr)(0), "///")(1)
.Start = .Paragraphs.First.Range.End
Set DocTgt = Documents.Add(Tmplt)
With DocTgt
.Range.FormattedText = Rng.FormattedText
.SaveAs2 FileName:=FlPth & StrNm & Ext, Fileformat:=Fmt, AddToRecentFiles:=False
.Close False
End With
End With
.Collapse wdCollapseEnd
.Find.Execute
Loop
End With
End With
Finished:
Undo: Set Rng = Nothing: Set DocTgt = Nothing: Set DocSrc = Nothing
Application.ScreenUpdating = True
End Sub