Continuing trades on signal irrespective of direction

I would like to continue the trades based on a signal, irrespective of the direction of the trade. Say for example, when STO is 90, first enter sell with 0.01, then enter buy with 0.02 with STO of 10, then enter 0.03 sell at STO 90. So 1 buy, 1 sell, 1 buy, 1 sell,..based on signal with increasing lot size. And then close all the trades when achieve certain amount of profit. 

I just STO as an example. It can be any indicator. Hope this can be useful.