How to change database data on second page based on what i select for the dropdownlist on the first page?

I have this 2 tables called room and schedule which have relationship with each other. Currently I only have lecture Room type. After clicking lecture in the first drop down list in mainmenu.aspx, the second dropdownlist will populate whatever rooms that belongs to lecture.
The problem is whatever rooms i clicked, either L338, L339 or L340, it always gives me the same output data on the timetable.(using daypilot control for the output) The output that I would like to achieve will be, L338 will come out only Lecture on network data, L339 will come out only Lecture on english data, and L340 will come out lecture on Chinese data.(see database data)
The room number on the title for number2.aspx will always changed because i stored it in a session on the mainmenu.aspx second dropdownlist, that's why the room number will always change. But I don't know how to make the data to always change based on the room number i select.
Room table and relationsh ...