I need an Expert Advisor who sets the trend with bar mapping

"For example, if I execute a sell order at the price shown in the image I sent, will the trade be opened exactly at that price, or will there be slippage because the actual market price is different? ​If slippage occurs, at what price will the trade execute when I click 'sell,' and at what price will it close when I exit the position? Also, is it possible to add another line to the chart that shows the actual price