Bom dia BuG5s,
Segue links de como fazer:
http://www.ehow.com/how_5201455_make-calculator-visual-basic.html (ver o passo 7)
http://www.wikihow.com/Create-a-Simple-Calculator-in-Visual-Basic-6.0
http://www.vbasic.net/how-to-create-a-basic-calculator-in-visual-basic-net-3/
Abraço