This type of thing doesn't actually use RegEx: Try:

Sub ScratchMacro()
'A basic Word macro coded by Greg Maxey
Dim oRng As Word.Range
  Set oRng = ActiveDocument.Range
  With oRng.Find
    .Text = "([0-9]{1,})( )(l[!a-z])"
    .Replacement.Text = "\1" & Chr(160) & "\3"
    .MatchWildcards = True
    .Execute Replace:=wdReplaceAll
  End With
End Sub