If you make the decision during the course of your interview that you’re interested in the opportunity your best course of action is to make a declarative statement.  “I’m very interested in this opportunity and I’d like to move forward.  Do you have any questions or concerns that I can address for you?  What’s the next step and when should it occur?”  Notice that you have not accepted the unacceptable or left yourself without recourse for the standard questions that arise during the course of the contract process.  What you have done is express your legitimate interest and human nature being what it is if you like them, they will like you all the more in return.  You want to make sure that before you leave the interview you know what their plan is so you’re not left waiting around wondering if they are going to get back to you or not!