Public Class Form1
    Private PG_ProcessID As Process
    Private PG_app As String = "notepad"

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

        Process.Start("notepad")
    End Sub

 
    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Dim currentProcessId As Integer = System.Diagnostics.Process.GetCurrentProcess.Id

        Dim pProcess() As Process = System.Diagnostics.Process.GetProcessesByName(PG_app)

        For Each p As Process In pProcess

            If p.Id <> currentProcessId Then

                p.Kill()

            End If

        Next
    End Sub

  
End Class