Cat Urine Smell

I have been dealing with cat urine in my furniture, I've shampooed, used Kids N Pets, Febreze, etc. I was able to lighten the smell, but not totally get rid of it. I found out my sister in law is highly allergic to urine smells, and my brother and her are going to be staying with me for a few days when they visit. I need to find something to get rid of this urine that is inexpensive and really truly works well. Any suggestions? Please? I need to do this within two weeks! HELP PLEASE!?! thank you.

Oh and in case someone decides to give stupid answers like get rid of the cats, no, this happened as an accident, I have an old cat who is going downhill, but is not suffering so I won't put him to sleep yet. He's very happy and healthy, just old. All other answers, thank you very much for your input.

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