Yes, it's the same with every other exchange. If your funds are already in a buy/sell offer, it's pretty much already sort of "planted" in the orderbook hence why you cant use the same funds to create a different order.
Thank you. But that's quite stupid, isn't it?
So how do the Youtubers that do swing trading do it? Do they have to sit in front of their computer all day?
OK, apparently Binance has this feature built in, an "OCO order".
https://academy.binance.com/en/articles/what-is-an-oco-order
That's fine, I was thinking of moving there anyway due to the higher volume.
Thanks everyone, think we've solved the issue!