Dropdown list in the form UIBB

Hi All ,

I have 2 plant fileds(werks) in the form UIBB , Dropdown list

If the user selects some input from 1 st dropdown

If user selects the 0003 from site and if the company code is 0001 , then i need to take the store which has company code as 0001 and display in the dropdown list of the house.

But here i am facing a problem ,I am populating the fixed values in the form class get definition , I have build the fixed values for the Site field , and after i select a value 0003 in site ,

How can i populate the fixed values for the house field , ? I think i need to create actions for site , but anyway i may need to write the logic in process event , but the fixed values we can build in the get definition ,

My question is where i can write the code for house field fixed values ?

Thanks,

Pradeep.