Chage Gross profit in Trailing

Hey guys,

I am busy with developing an EA. I want to add a function which I cannot do by myself.

 Now there is a profit setting in the EA. One can set a predetermined value in dollar (so not pips) and when that profit is met all open positions will be closed.

So we do not use TP for individual trades neither use pips. We only use total usd profit in settings.

I want to change that so it becomes trailing. In other words I want settings so that if a certain level of total profit is reached, it moves and secures profit when market is moving in my favor. 

 So sort of trailing gross profit.

 There are loads of sl trailing stops ea etc. (multi purpose man) but I cant find trailing profit in gross usd. 

 Please think with me and let me know...

 grtz