"I am working with a large spreadsheet of contact information for people in my industry."
That isn't what Excel is for. Excel is for calculations, not data keeping. Use a Database.
Are you familiar with the concept of a Database?
You store values in tables, then report on the values. Exactly what you are trying to do.
May I suggest, you use a value to store the area of interest, instead of just an X. That way you can survey your sampled base and see HOW interested, not just IF they are. Then you can report on users that are interested in a particular area, with a value of X; or N or better.
Just a thought!
If you choose to go the Excel route, it can be done, but how much coding experience do you have? If you have none, then I would suggest learning the concepts of a Database!
Then just write reports on tables. No Coding Needed!