left padding with zero in siebel.

I have a requirement in siebel Where user is putting value in text box like 5-6-78-4. and i have to pad it with zero like ..05-06-078-4.How can i implement it. Any idea how i can implement it with regular expresion. I have regex for  match "/([0-9]{2})\-([0-9]{2})\-([0-9]{3})\-([0-9]{1,3})/g". But dont know how to pad with left zero if it doesn't match.