Automating Programs

[Crzyrio]

this is how to start notepad with no window, print the document, then exit:

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim psi As New ProcessStartInfo With { _
        .FileName = "atextfile.txt", _
        .Verb = "Print", _
        .CreateNoWindow = True}
        Process.Start(psi)
    End Sub


End Class

What if it is not a regular format? It is a 3rd party program with a non standard extension.
How would I specific what program to open?