Double click on the commandbutton and you'll see this type of code:
Option Explicit
Private Sub CommandButton1_Click()
End Sub
Just change it call your old macro:
Option Explicit
Private Sub CommandButton1_Click()
Call youroldmacronamehere
End Sub
(You'll have to be in design mode (also on the control toolbox toolbar) before
you double click. And remember to toggle design mode off when you're done.)