Having one process run another process at timed intervals
if(!ProcessA.isRunning)
    ProcessA.Run();
else
    Wait Until Next Interval to try

// Get all instances of Notepad running on the local
// computer.
Process [] localByName = Process.GetProcessesByName("notepad");

var startOtherProcess = true;
    while (startOtherProcess) {
       var watchedProcess = Process.Start("MyProgram.Exe");
       watchedProcess.WaitForExit();
       if (testIfProcessingFinished) {
           startOtherProcess = false;
       }

    }

[DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool SetForegroundWindow(IntPtr hWnd);

    public void RunProcess()
    {
        bool createdNew = true;
        using (Mutex mutex = new Mutex(true, "MyApplicationName", out createdNew))
        {
            if (createdNew)
            {
                // Here you should start another process
                // if it's an *.exe, use System.Diagnostics.Process.Start("myExePath.exe");
            }
            else
            {
                Process current = Process.GetCurrentProcess();
                foreach (Process process in Process.GetProcessesByName(current.ProcessName))
                {
                    if (process.Id != current.Id)
                    {
                        SetForegroundWindow(process.MainWindowHandle);
                        break;
                    }
                }
            }
        }
    }