Well, being up front with him isn't going to work, but it was admirable that you took that route to start (although perhaps the reason he didn't accept your offer was that he was insulted). I'm guessing that since Curve is for special occasions, and that his signature coffee-smoke-febreeze scent combo includes Brut 33, then he's not really wanting to spend a lot of money for his daily routine.
Find a good knockoff of Curve. I don't know where you live, but there are places around here (the flea market in my area) that I can buy replicas of pretty much all the major scents. They're all about $5-10. Tell him you bought a different knockoff of a cologne you already wear just to see if it was close and that you thought you could save a little money in doing so. Say that you saw the Curve copy, thought of him, and figured you could save him a couple bucks too. If he tries the Curve right then, enlist the help of a trusted co-worker. Let them know in advance what you're doing. Have them walk by him, stop, kind of sniff, and then ask him if he's wearing Curve. They can compliment the scent, and then just move on. He might enjoy the compliment, and just convert it to daily use from that point forward.