Forms :: Checkbox / List Box And Unbound Keyword Search

I'm relatively new to Access 2010. I have an excel spreadsheet that I've converted into an access table for the purposes of creating a user friendly form for the end user to search for relevant criteria to retrieve a list of records that fit the requests. There are two main search functions: unbound keyword search (90+ keywords), and either a series of checkboxes or one list box that lists specific countries/regions matched in a column (columns, as I will get to shortly). The region selection is bound by a selection of 15 countries.

The key is each record can correspond to more than one country. This, one record can have "Belgium, Germany, brazil" and the next record can just have "brazil". Thus if someone selects brazil, the query must retrieve the Belgium Germany brazil record in addition to the record that covers just brazil. I've tried to do this with a concatenated column that list all countries and a text box search, I've tried to do this with individual checkbox columns for each country with checkboxes in the search form...and I can't get it to work. I don't fully understand the criteria to set for checkboxes or list boxes. What would be the best way to build this form, an how?