Screen validations in webdynpro java (NWDS 7.0)

Hi Experts,

We are using Portal 7.0 version and NWDS 7.0, we have developed one wdj application .in this application  i have designed one dropdown key with "YES" or "NO" options.

if user click on YES ,then i should be ask the Enter the amount and after enter the amount i will go to another dropdown key field(department list field) with yes or no values, same thing procedure repeat for this dropdown field(department list field)also.

If user click on "NO", it should be go for direct next dropdown field(department list field)..

Please help on this issue.

Regards,

Vanitha