Create a single button with a single function

Hi 

I want to have EA or Script or Indicator that will give me button to press which will close half my open order without having to open any other window or click more than once.

So if I have a open position of  1.00 and click the button the half the order must be closed at the next available price so 0.50 will be closed and 0.50 will be left open

Please see picture and ask questions if you are interested