“I’m just a man, I can’t help feeling like that”

Well yes, but I’d kind of extend that to being just a person, able to control my actions but not feelings.

OP didn’t say he was fighting his instincts not to bend her over and give her a good deep dicking because her fly was down.

I personally find any kind of close proximity with a professional of any gender or age to be quite uncomfortable.

I would find it even more uncomfortable if their fly was down or whatever.

I would find it even more uncomfortable if the professional in close proximity with their fly down might think I was being inappropriate by noticing that their fly was down - an outcome much more likely if that person is an attractive young lady.

That said, you have some odd ideas about being older and being married. I’m in my mid 40s and have been with my partner for 15 years or so. I still find people in their 20s and 30s physically attractive, just like I did when I was 20 . Also my commitment to my partner does not mean I am magically blind to attractive people around me.