Wow, I don't think I'd ever even consider entering 40 new contacts into a phone while at a meeting.
Here's something you can do, though. Create a new group in iCal called something like meetings, or the company name, or the matter on which you're going to meet, or just iphone-added. Then when you go to enter new contacts into the iphone, just make sure you tap new when you're in that iphone-added group.
The first benefit is that all your 40 contacts will be grouped in that group, so it'll be easy to find them.
The second is that when you get back to your computer you can drag them into your regular groups where you'd like them to be, and also keep them in the iphone-added group, or maybe make a new group named for the matter and move them there and delete them from the iphone-added group, so they'll still be grouped together in the new group, but will also appear in All Contacts and any other group you've put them in.
Since I have a lot of contacts, I've made extensive use of groups to keep them organized, and I've found that really paid off for the iphone.
Smart groups won't sync, so I've also used smart groups to find, say, all contacts from a particular company or set of companies, and once the group is populated, I can then make a real group named for that company and copy them all in from the smart group into the newly named group. Then delete the smart group.