Complex Customized Element Block in Form

I would like to build up a complex element with a bunch of dependent dropdown lists and textboxes with events triggered from a choice element.

Say for example, the process flow on that element would be as below:

1. users pick a choice on the choice element.
2. based on the selection of the choice element, a grid shows up.
3. The grid has Add button and Delete button. Users can use that Add button to add a new line into the grid or use the Delete button to remove the existing record from the grid.
4. The record line contains textfield and a couple of dependant dropdown lists. Users use them to intput and edit that record content.

Hopefully I describe clearly.  Requirement is a little complicated. 

Any idea or advice?

Thanks so much in advance.