A While Loop in a path finding system is freezing, how can I fix this?

I am developing a custom path finding system for a four-way grid. At this point, I have nodes that have neighbors, a starting point and a end point target. I am attempting to work out the path between the start and end - four way only, NOT diagonal, and then run the path, but the loop is freezing - with barely anything in it. In order to prevent a total game crash I inserted a time check, but it doesn't stop the game itself from pausing until the system breaks the loop. The code for the current path finder is below:

     void PathFinder()
     {
         // Find Target Point //
 
         GetBoardPosition();
 
         int TargetX = TargetSquare.X;
         int TargetY = TargetSquare.Y;
 
         int CurrentX = lastSquare.X;
         int CurrentY = lastSquare.Y;
 
         bool IsTrue = true;
 
         // Get Current Board state //
 
         Squares[,] GameBoard = new Squares[BoardSize, BoardSize];
 
         for (int widthTraveled = 0; widthTraveled < BoardSize; widthTraveled++)
         {
             for (int heightTraveled = 0; heightTraveled < BoardSize; heightTraveled++)
             {
                 Squares PointEval = System_GameController.Instance.GameArray[widthTraveled, heightTraveled].GetComponent<Squares>();
 
                 if (PointEval._cellState == cellStates.isEmpty)
                 {
                     PointEval.Cost = 1;
                 }
 
                 if (PointEval._cellState == cellStates.isOccupied)
                 {
                     PointEval.Cost = 100;
                 }
 
                 if (PointEval._cellState == cellStates.isX)
                 {
                     PointEval.Cost = 50;
                 }
 
                 if (PointEval._cellState == cellStates.isO)
                 {
                     PointEval.Cost = 50;
                 }
 
             }
         }
 
         lastSquare.Cost = 0;
         TargetSquare.Cost = 500;
 
         // Check if neighbors that are closer to the target have a cost of 1 //
 
         bool FoundMoveTarget = false;
 
         List<Squares> ClosedSquares = new List<Squares>();
         List<Squares> OpenSquares = new List<Squares>();
 
         System.DateTime CurrentTime = System.DateTime.Now;
 
         OpenSquares.Add(lastSquare);
 
 
 
         while (OpenSquares.Count > 0)
         {
 
             if ((System.DateTime.Now - CurrentTime).TotalMilliseconds > maxSeekTime)
             {
                 Debug.Log("Seek Time Exceeded.");
                 break;
             }
         }
 
     }