Adding Form Object dinamically

I just have the need to add objects in a form in a dinamic way.
i just give an example:

i have a dropdown box and a text field, and the final user have to add
as many copies as they wants of this dropdowbn box and text fields
the results will be emailed to x other users

how can i handle this situation?

If by "dinamic" (sic) you mean without a page refresh, you'll need to
use JavaScript.

I'd think any decent JS tutorial would cover creating elements and
adding them to the page's DOM.

Or are you saying you currently have some code that's failing?