I work marketing some of the most beautiful women you can imagine are hanging out around my desk all day NOT because they are in love with me because they have a job to.
So the question becomes how to generate attraction SUBTLETY in the work place
From your post your obviously still in school (high / college) when your conducting business with a woman that you want to get involved with romantically women in the work place are attracted to 3 characteristics above all:
1) Confidence - I will make the sale, I will bring the account home I will make sure the team does well on this project. Why? Not because I'm trying to impress you, because I'm a winner and that's what winners do is bring home the V (stands for Victory in the business world but you can use your imagination...

)
2) Control
Comprised of 3 elements:
Discipline: meet your deadlines no matter what you show up on time on matter what.
Patience - Let the client move at there own pace realize that NO ONE does this game better. And let them come to you. Women see this and subconsciously say this is a powerful man that is in high demand people want the privilege of knowing him.
Self-Control: Yes your hot I know this as you know I am hot as well but we have a job to do. If you can be the one reminding her of this fact your ready be ready to pounce after the the conclusion of the of the deal.
3) Challenge: you don't give away the store! You treat he just enough as a woman that she doesn't think your cold, gay, or a workaholic. But enough like a member to a the team that slowly she is building respect for you and respect leads to desire.
The reason I said you need to re-get her phone number is because she was FORCED to give it to you. Just like currently she is FORCED to spend time around you. Building attraction in the work place is NOT the same game as in a bar or social gathering. If you
display the male control factors above she will be drawn to you (as well as any woman watching that) can then she will want to be around you. That is when you re-get her number this time there is no confusion about why your getting it and why she's giving it to you.