While I don't have a "don't play at work rule", I do try to avoid it. It makes things difficult no matter how much of adult you are.
Its also tough, if you work 8 to 10 hours a day, you can in fact see co-workers more than lovers. Its easy to build a rapport with co-workers. I have been involved a few times with co-workers...its only gotten bad with one but that was all on me, I could not control my feelings at times. Very unprofessional. I am very social with co-workers in general so I intermix a lot.
You could simply lay it on the table. I am interested in you and my boyfriend approves. Or something like that. Might as well do it while there is interest and not hide it. If interest continues then you might have something