You could use an autocorrect entry, but unlike the hyphens, there is no built-in function to do that.
Maybe a macro would help?
Code:
Sub Macro1()
Dim orng As Range
Set orng = Selection.Range
Do
orng.Text = orng.Text & "*"
If orng.Characters.Last.Information(wdVerticalPositionRelativeToPage) > _
orng.Characters.First.Information(wdVerticalPositionRelativeToPage) Then Exit Do
DoEvents
Loop
orng.Characters.Last.Delete
orng.Collapse 0
orng.Select
Set orng = Nothing
End Sub