yes, that's correct, something like that (I assume you've added the reference to Microsoft.WindowsMobile.Telephony)
Imports Microsoft.WindowsMobile.Telephony
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim myPhone As New Phone()
' I've added a textbox to the form to collect phone number
myPhone.Talk(TextBox1.Text)
End Sub
End Class