Javascript implemented in PHP/Mysql to populate 3 comboxes

hey comrades, thanks for sharing these priceless resources here. i like them and for that i decided to join the community.
I have read an article regarding displying related records in 2 comboboxes. i however would like any memeber to help add the third combobox to display related records according to the selection made in the second. In brief, i would like to modify the code the that displays related records in 2 comboboxes to the one can display related records in 3 comboboxes. thanks. awaiting for the reply.