The prices you see within MetaTrader 4 are the “Bid” prices, i.e. the price to sell. When you are executing a sell order, your orders are executed using the “Ask” price. You can see both the current live bid and ask prices within MT4’s “Market Watch” window. However, historical ask prices are not available.  

 

To see Ask line as well right click the chart and go properties (or press F8), switch to "common" tab and tick "Show Ask line" box. 

 

Remember that the difference between these two prices (bid/ask) is what is called the ‘spread’. Please take this into account when you’re placing your pending orders or stop losses/take profits.