Call Procedure From Add-in

I have a userform in an add-in (which is loaded), when I try and call it from an excel sheet, I get the following error "Variable not defined"

Private Sub CommandButton3_Click()


UserForm1.Show


End Sub

The code in the userform is all private subs.

Similarly when calling a public sub from the add-in such as;

Private Sub CommandButton3_Click()


Call SillySub


End Sub

I get the error "Sub or Function not defined".

How should I be doing this?

Re: Add-in Userform Gives Variable Not Defined

http://www.fontstuff.com/vba/vbatut08.htm