What you describe sounds like a conditional value list with a slight twist--that the match field is formatted as a check box field. That should work quite well if you want select both "conference" and "Meeting" types and then get a list of both types in the same list. This is due to the way match fields that contain return separated lists of values--what a check box field of this type creates when you click more than one box, match to records in the related table.
Here are some links on condiitional value lists:
There's a lot of overlap between the first two links so you can read one and skim the other. The demo file gives you several examples of different conditional value lists so you can examine them to see how they are set up. If you are using FileMaker 12, you can open this demo file from your File menu to get a converted copy of the demo file that you can examine in FileMaker 12.
The last link discusses how to set up a chain of conditional value lists where the value selected in each conditional value list controls the values listed in the next value list.
Forum Tutorial: Custom Value List?
Knowledgebase article: http://help.filemaker.com/app/answers/detail/a_id/5833/kw/conditional%20value%20list
Hierarchical Conditional Value lists: Conditional Value List Question
Feel free to post follow up questions here if those links aren't enough to get your value lists working correctly.