Check and open maximum position of symbol

Hi,

im not good for coding, i have an idea, but i dont know how to coding: check 10 symbols (EU, GU, GJ, AU, NU, UCAD, UCF, GA, EJ, AJ) if one of them have price is crossing  EMA21 then buy/sell. But just opened 6 symbols at the same time. , if position of one of 6 symbols is closed, other symols will be checked again.

Thanks in advance