How to get Checked Values from Facets-CheckBox Group?

I'm using ORACLE APEX "Sample Maps" example on the "120 - Airports Faceted Search" page. I need to get the checked options from Facet "P120_STATE" (it's a checkbox group) and put this checked values in a Text Item called "CHECKED_STATES". I don't know how to get the checked values in this facet checkbox group. I need to get these checked values to use in another SQL command, for example:

select CITIES.ID as ID, CITIES.NAME as NAME, CITIES.STATE_CODE as STATE_CODE from CITIES CITIES where STATE_CODE IN ( :CHECKED_STATES )