Non obstructive wait

Question

Hi All,
I am trying to perfect a bit of test code for a device we have updated (amongst other thing replaced a 9 Way with USB) I want to a method of waiting for a command to come back,the  routine waits while there are no bytes in the buffer and the time is less the value passed to it. NbDataToWait is a bit vague I would prefer to wait for '>' come back  but can't seem to think of a way to do it quickly!
    public int WaitForData(int NbDataToWait, int Timeout)
          {          
                        int timeWaited = 0;
                        int timeToWait = 1; // 1 ms
                       
                                                                                     // && there is no > in reply
                        while (timeWaited < Timeout && myComPort.BytesToRead < NbDataToWait)// && myComPort.BytesToRead(">"))
                        {
                            timeWaited += timeToWait;
                            lblwhere.Text += ".";
                            System.Threading.Thread.Sleep(timeToWait );
                        }


            return timeWaited;


        }
  /* public int WaitForDataOK(int NbDataToWait, int Timeout)
        {
            int timeWaited = 0;
            int timeToWait = 1; // 1 ms


            // && there is no > in reply
            while (timeWaited < Timeout &&  myComPort.BytesToRead > 0)
            {
                timeWaited += timeToWait;
                lblwhere.Text += ".";
                System.Threading.Thread.Sleep(timeToWait);
            }


            return timeWaited;


        }
         */
UPDATE::  I believe I need to wait  for a >