@guiguito,
And now the real truth comes out.
Don't be stupid. Having an affair with someone at your office is a bad, bad idea. Don't want to be married? Then get a divorce, and give your wife a chance to find someone else.
As for you, you're sounding now like a guy in the throes of a midlife crisis.
News flash: not everyone who's nice to you or smiles at you wants to sleep with you. And people who are polite to you aren't a good reason to destroy your marriage.
End your marriage if you must, but don't go coming here looking for permission to hurt others.