WebDynpro custom search help based on another field value

Hi,

I need to have custom search help for field2 based on selected value of field1. Here field1 is parameter and field2 is select-options. here field one is material and field2 is division. Bydefault we are getting the standard search help for Division but needs to be filtered based on the material which is entered by user.

I found few ways, one of it is creating search help and DD and assign that to the field2, we dont want to do that since this custom help will be needed only for this screen, so wants to write the custom logic to get filtered divisions and need to assign to the select-options.

Thanks