Placing orders based on underlying price

I have a question, how do you guys place a limit order on an option based on stock price? For example, I'm using ToS platform and I could place an order based on a stock price but how would I know the price of an OPTION when stock price reaches my target.

For example, I want to sell a put option at $100 strike when stock goes down to $100 from current price of $110 but how would I know which limit price to enter since I don't know exactly what option prices is going to look like at that time? The reason is that I just want to put a GTC order and let it execute if I'm away or asleep. Ofc, I could just do a market order when stock hits $100 but is it a good idea? I guess I could also do an estimation using ToS risk profile tools.