How to Create Cascading Parameter in BIRT?

Dear All,

Kindly request you to all if anyone can tell how to populate second parameter based on the first parameter.
e.g.
DataSet_state
v_state_code
v_state_desc

DataSet_branch
v_branch_code
v_branch_desc

I have create New Cascading Parameter Group but not getting the values.

Please advice with full example

Regards,
Satinder Kumar