Put this after the class declaration and any constant/variable declarations:
'The SetForegroundWindow function puts the thread that created the
'specified window in the foreground and then activates the window.
<DllImport("user32.dll")> _
Private Shared Function SetForegroundWindow(ByVal hwnd As IntPtr) As Boolean
End Function

The following is a menu click event for bringing an application called RespEditor to the front if it is running or else starting it.
Private Sub mnToolsRespEditor_Click(ByVal sender As System.Object, _
              ByVal e As System.EventArgs) Handles mnToolsRespEditor.Click
     Dim myProcesses As Process() = Process.GetProcessesByName("RespEditor")
     'The path to RespEditor.exe is stored in Settings.
     Dim respEdPath As String = My.Settings.RespEditorPath
     Dim result As Boolean
     If (myProcesses.GetUpperBound(0) > -1) Then
          result=SetForegroundWindow(myProcesses(0).MainWindowHandle)
     Else
        If File.Exists(respEdPath) Then
             Process.Start(respEdPath)
        End If
     End If
     myProcesses = Nothing
End Sub