Script to trail the breakeven

i want a breakeven that work as trailing stop 

as example : i need to set a target profit and stop loss.

setting in the script:

- 1)At X pips in profit increment with Y lot position.

- 2)At X pips in profit increment with Y lot position.

- 3)At X pips in profit increment with Y lot position.                   

- 4)At X pips in profit increment with Y lot position.

- 5)At X pips in profit increment with Y lot position.

- 6)At X pips in profit increment with Y lot position.  

Draw a breakeven line and move stop loss to breakeven anytime we will increment lot position.

Example : buy with 300 target profit and 100 stop loss with 0,1 lot size.

-1)At 50 pips in profit increment buying again with +0,1 lot size .   In the meanwhile script will move stop loss to breakeve that is now at +25 of the initial trade.

-2)At +100 pips in profit increment buying again with 0.5 lot size . in the mean while script will move stop loss to breakeven again, calculating it.

-3)At +170 pips in profit increment buying again with 0.8 lot size.   in the mean while script will move stop loss to breakeven again, calculating it.

And so on...

I want to decide how many step to increment, with a maximum of 8 steps.

I want to test it  in backtest of metatrader.