convert custom indicator to EA (expert advisor)

Hi .. I have a custom indicator that gives sell and buy alerts. I want to convert it to EA that convert these alerts into orders as follows " @@ when a buy signals comes, it closes the sell order and opens a buy order. @@ when a sell signal comes , it closes the buy order and open a sell order. depending on these two rules above : @@ the the maximum opened orders at the same time is always only one trade. @@ there is always a trade opened. @@ I have to be able to set a default lot size to the orders. note : when the ea is launched it must check if there is order opened or not, to make sure not to open more the one order at the same direction. ## what I need is to convert the code itself from an indicator code to EA code ( the use of icustom function is not allowed ) ## @@ there are two versions of the indicator. one for the 4-digit metatrader, and the other for the 5-digit. so I'm expecting the same thing for the EA. you can contact me if any further information is needed . The parameters of the indicator is as flowed Ext Depth 20 Ext Deviation 5 Ext Backstep 3 Or can be able to adjust the previous 3 setting if possible if you can add adjustable lot size, stop lost and take profit it will be great or money management, along with time filter. Please feel free to contact me Thanks