database and combobox

Hi,In my application ,there is a combobox in which classname appears .
Now I want that for each selected classname from combobox,I want that user could add sections according to his wish .
Like if user selects class1 and he wants to add 4 sections(A,B,C,D) .he should add "A" in "section name" click on add and "A" should display in table below.
in this I want that user could enter section according to his wish.
After adding all sections, when user selects any classname from combobox1 then the corresponding sections should display in combobox2.i.e. for each selection of classname corresponding sections should appear in another combobox...........
The database which I am using is MS Access

Also,the same sectionname can be added to more than one class?
eg, Class 1 - Section A and Class 2 - Section A.
Two different classes can have same section name but they should be different.

Kindly help me..........