Happened to me last week.
I went for an interview and was discussing my credentials with an attractive young woman. She was dressed very professionally, but with a pushup bra and a top with a low neckline. The cleavage was most impressive.
I temporarily found myself having a Homer Simpson moment... "Don't look, don't look, don't look, D'OH!!!" I suppose it was better than drooling on myself and thinking..."Mmmm, boobies." I give myself a B-.