public void LaunchRPGApp(Application program)
{
    var processInfo = new ProcessStartInfo("pcsws.exe")
    {
        WindowStyle = ProcessWindowStyle.Normal,
        Arguments = ""C:\Program Files (x86)\IBM\Client Access\Emulator\Private\veflast1.ws"",
        RedirectStandardInput = true,
        UseShellExecute = false,
    };
    var process = Process.Start(processInfo);
    if (process == null) throw new Exception("Error starting process.");
    using (var sr = process.StandardInput)
    {
        sr.Write("f");//does nothing
        sr.Close();
    }
}

[DllImport("user32.dll", EntryPoint = "FindWindowEx")]
public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
[DllImport("User32.dll")]
public static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, string lParam);
private void SendTextToProcess(Process p, string text)
{
    const int WM_SETTEXT = 0x000C;
    const int WM_KEYDOWN = 0x0100;
    const int F_KEY = 0x46;
    Thread.Sleep(500);
    var child = FindWindowEx(p.MainWindowHandle, new IntPtr(0), "Edit", null);
    SendMessage(child, WM_KEYDOWN, F_KEY, null);//does nothing
    SendMessage(child, WM_SETTEXT, 0, text);//does nothing
}

ProcessStartInfo startInfo = new ProcessStartInfo("pcsws.exe");
startInfo.WindowStyle = ProcessWindowStyle.Normal;

startInfo.Arguments = "C:\Program Files (x86)\IBM\Client Access\Emulator\Private\veflast1.ws";
Process.Start(startInfo);