Bring A Large Pot Of Lightly Salted Water To A Boil. Place Spaghetti In The Pot, And Cook 4 Minutes. Mix In The Broccoli Florets. Continue Cooking 4 To 6 Minutes, Until Spaghetti Is Al Dente. Drain, And Transfer To A Large Bowl. Melt The Margarine In A Skillet Over Medium Heat, And Cook The Chicken And Onion 5 Minutes, Until Chicken Juices Run Clear And Onions Are Tender. In A Bowl, Whisk Together The Soup, Milk, Water, And Cream Cheese Until Smooth. Stir Into The Skillet With The Chicken And Onion, And Bring To A Boil. Reduce Heat To Low, And Simmer 5 Minutes, Or Until Slightly Thickened. Toss In The Bowl With The Spaghetti And Broccoli To Serve.