I have everything working as expected in auto-trading my strategy in paper account, I would like to ask if it put into the real account, is it allow me to place unlimited no. of buy limit orders in real account?

Let me explain it by an example. I got $500000 in paper account and my strategy automatically run at 5% of capital in S&P600, the strategy generates 100 buy at limit orders in the same day, I am allowed to place all limit orders in paper account, and the orders are done until all my cash used up, therefore I can get those symbols first hit the limit price and leave the reminding symbols unexecuted because insufficient of cash.

I wonder if this can be done in real account. Once I put first 20 limit orders in my account, it has already used up all my cash as each spends me 5% of my capital, and leaves 80 limit orders even not able to placed in the account.

Would your broker allow placing limit orders in excess of your capital IRL (in real life)?

Use the Quotes tool. It's designed to monitor hundreds of triggers and send only the alerts to market that are triggered at or near the stop/limit price. See the User Guide for details.

Thank you both Eugene and Cone, I will try it then!!