I think you would basically have to create an HTML field type and then include an input button via HTML (basically plain HTML... then an input button just like you have in your example here, and finally add an onblur event to update a hidden field on the form). You would have to ...
1. Generate the input button and maybe initially make an onblur event just do a popup to make sure its working.
2. Find the actual hidden field or textbox for a Dynamic Forms instance and update that field with your step #1 onblur event.
When the form would submit you could then capture the hidden field from #2 and verify that it was submitted/required etc...
Client side events can be pretty tricky but you might check out this demo:
http://www.datasprings.com/Products...fault.aspx In that example we include a 'textarea' object within an html template.
We can also code this for you directly if you need us to write the client side event with Premium Support. You can pick up hours and assistance at
http://www.datasprings.com/Premium-Support. Thanks!
-Chad