Custom field to define the type of event

Dear all,
I am using directory response theme and I want to have website with a list of events. I made categories and subcategories based on the “subject” of events ( eg: plant science, animal science and mathematics etc). Now each event may fall under certain “type” Eg Conference, Meeting, Symposium or Workshop. How can I incorporate this categories also and make it selectable in the advanced search? Eg: all events which is under plant science and either meeting or conference?
I thought to define a new custom field as “type” and when user add an event, he/she defines what type of event it is.
Is this the right way in the architecture of Directory? In future I want to use this “type” to only show certain type of event on home page etc..

please guide me through this.