What you need is
Code:
Sub rtf_test()
Dim oDoc As Document
Dim strPath As String
Set oDoc = ActiveDocument
oDoc.Save
If Not ActiveDocument.path = "" Then
strPath = ActiveDocument.FullName
strPath = Left(strPath, InStrRev(strPath, Chr(46))) & ".rtf"
oDoc.SaveAs2 FileName:=strPath, FileFormat:=wdFormatRTF
Else
oDoc.SaveAs2 FileName:="Filename.rtf", FileFormat:=wdFormatRTF
End If
Set oDoc = Nothing
End Sub