From a user experience perspective, you should have a landing page they'll go to after they click. Something like "Thank You for Your Interest, we'll be in touch shortly" Set up your email so that a click on your "Interested" button goes to this landing page. Note the URL
Then, to know who clicked, set up a Smart list
1. Use a Filter: "Clicked LInk in Email"
2. Select your Email from the menu.
3. If desired, clidk the "x" to remove "Date of Activity"
4. Click "Add Constraints"
5. Check "Link"
6. Select the link for your landing page from the drop down menu
7. Click "Leads" in the 2nd menu bar at the top of the screen (to the right of "Smart List")
You'll now have a list of everyone that clicked.