Dependent ComboBox

Hi,
I have a little problem regarding combobox, I have 4 combobox dependent to other combobox something like this. First combobox populate from MSSQL using asp?
But my problem is how can I put populate the 2nd combo box with selected item in combo box 1?

1st combo
Island

2nd combo
Province

3rd combo
City/Municipality

4th combo
Street

Please help…
Thank you and God Bless…