Limiting the number of contacts who enter a Smart Campaign

Hello,

I've been searching the community to see if there is a way to put a limit on the number of people who run through a smart campaign. We are running a survey and providing an incentive to the first 300 people who fill it out. We would like to send one thank you, congrats! email to the first 300 people who complete the survey/trigger the smart campaign and send a different thank you response to those who don't qualify.

Is something like this possible? If not, is there a way to track the order in which respondents join a smart list so I could easily segment the first 300 leads who responded?

Thanks.

Kari