How to get wee smell out of carpet?

Poppy has a habit of weeing in the same corner of our living room at the moment. I'm going to lock the door from now on but does anyone have any "recipes" for homemade carpet cleaner that gets rid of wee smell? The bought ones are so expensive and smell horrible and I'm sure I could make one myself.
Tips welcome!!

cold solution of biological washing powder/liquid.

Bicarb is great for removing odours we use it like shake n vac, apply it dry to the area and give it a gentle brush, leave it for a while then hoover up

urine off is a good product but very expensive. I have tried Bicard and all the normal things sold in pet shps to no avail ... but Urine off does work

Vinegar is good with odours, mix 50:50 with water. White vinegar smells a bit less potent than malt! The vinegar smell doesn't linger for too long so don't panic about the house smelling like a chipshop

Thanks for your replies folks.....will give them all a try!!