Business Process Flow Fields Customization and Developement

Hi,

i am having fields in Business Process Flow How to hide and show these fields?

ex:my field name is "Bank Name" i could not hide this field using following script

Xrm.Page.getControl("header_process_new_bankname").setVisible(false);

another thing is i could not apply prefilterlookup to Business Process Flow Fields

ex: Prefilter "State" value Based on "Country" value

pls help me to achieve this