You cannot insert part of a field, but you can insert the path and filename on two lines with a macro e.g.
Code:
Sub InsertPathAndFilename()
With ActiveDocument
If Len(.Path) = 0 Then .Save
Selection.TypeText .Path & Chr(92) & vbCr & .name
End With
lbl_Exit:
Exit Sub
End Sub
If you want the name without the extension change
to
Code:
& Left(.name, InStrRev(.name, ".") - 1)
http://www.gmayor.com/installing_macro.htm