Sit in his lap and let him see what he's signing up for

You hop over your desk and straddle him in one motion. He moves to get up but you're pinning him down and his resistance fades. You laugh before diving onto his neck, grinding your firm ass all the while into his semi-hard cock

He's holding his breath. He's definitely not used to this kind of aggression. You butter him up with some playful teasing. You ask him if he wants to fuck you, but there is no response. He's almost catatonic and his erection is actually receding under your ass.

You stand up and tell him it's OK and he just needs to relax. You tell him you'll help him with that quickly work your way out of your small gray vest, revealing beautiful handfuls of breast nestled in a black demi-bra, as well as a subtle six pack of your delicious girl abs. You return to him and kiss him deeply, working your hands through his already tussled hair. His whole body is stiff but for the one part you crave. Without breaking your energetic kiss, you place his hands on your ass, forcing them to massage your firm glutes. Eventually he gets the hint and rubs them himself. With a lip bite and a lewd smile you squeal to encourage him.

Your head is on his shoulder as your hips grind. His hard cock is rubbing against your equally hard stomach muscles. You turn and put your ass against his stiff rod, laughing as your bob the crack of your ass, well defined by your tight pants, over his length. You encourage him to slap your hips. His first attempt is pathetic and you cajole him to do it as hard as he can. He takes a breath, then wallops your cheeks as hard as anyone ever has. You yelp in simultaneous delight and pain. You are glad you invested in soundproofing the office.

"Sorry!"

You grab him by the hair and kiss him again, telling him you loved it.

He seems ready now, but will he be worth the effort to fuck?