Let me help you a little bit.
A woman approaches you. Says she was interested you and would show you a good time. Is that lust on your part? Is it a sin to not commit adultery with her as is contended?
Let me help you out a big bit

as you're inventing a 'contention' that doesn't exist.
(it's a straw man argument, a logical fallacy no one needs to acknowledge)
You're focusing on the man and ignoring the woman. The man in your hypothetical situation is has a decision to render. He could:
1) locate another witness to the woman's action, and go through the process that would have her stoned to death.
2) wriggle his wedding ring in front of the woman's face and basically refuse her.
3) feed on the passion (aka lust) in his heart and decide two wives are better than one (sound familiar?) and follow through on his passion (aka lust).
Only one of these responses is in accordance to the Mosaic covenant Law you're promoting on this forum.
WWJD?
John 8
2 Now early in the morning He came again into the temple, and all the people came to Him; and He sat down and taught them. 3 Then the scribes and Pharisees brought to Him a woman caught in adultery. And when they had set her in the midst, 4 they said to Him, “Teacher, this woman was caught in adultery, in the very act. 5 Now Moses, in the law, commanded us that such should be stoned. But what do You say?” 6 This they said, testing Him, that they might have something of which to accuse Him. But Jesus stooped down and wrote on the ground with His finger, as though He did not hear.
7 So when they continued asking Him, He raised Himself up and said to them, “He who is without sin among you, let him throw a stone at her first.” 8 And again He stooped down and wrote on the ground. 9 Then those who heard it, being convicted by their conscience, went out one by one, beginning with the oldest even to the last. And Jesus was left alone, and the woman standing in the midst. 10 When Jesus had raised Himself up and saw no one but the woman, He said to her, “Woman, where are those accusers of yours? Has no one condemned you?”
11 She said, “No one, Lord.”
And Jesus said to her, “Neither do I condemn you; go and sin no more.”
12 Then Jesus spoke to them again, saying, “I am the light of the world. He who follows Me shall not walk in darkness, but have the light of life.”
13 The Pharisees therefore said to Him, “You bear witness of Yourself; Your witness is not true.”
I only highlighted a couple of the Pharisees' statements for simplicity.
Two questions to consider:
- When Jesus didn't condone what the Law required, what attribute did He display which is absent in the Law?
- Why did the Pharisees, who promoted adherance to the Law, reject Jesus?