How long do you have to look and think before it is sin? 5 secs? 10 secs? a minute ? ... how long before it is sin?
If you don’t lust and are earnestly seeking to conquer any temptation to lust, then you might hafve to look for a long time.
One can be placed in such situations.
As a cadet who spent a summer in Germany under the tutelege of s young lieutenant, I once went out in the big city with him as my ride and guide. We spent some time enjoying the night life. He kept insisting that he was going to “get me laid”. He was bothered by my loyalty to my longtime girlfriend (now my wife) and my chastity. He ended up going to a brothel (they are legal in Germany), knowing that I was dependent on him for a ride and to even find my way out of that section of town and back to my barracks since I did not know any German. Of course since this was a shady part of town I went inside the building, but I waited in the hallway for him and all sorts of tarted up sluts tried to encourage me to spend some of my money on the sexual favors they were selling.
This seemed to last for an hour. I will never forget the temptation and my determined victory over it through and for God.
The lieutenant never harassed me about my loyalty to my girlfriend or my chastity again.