I think you might get more answers in the developping forum, asking this.
But I'll give it an attempt.
NO. You need Webdialog for checkbox. (very sad indeed)
I'm guessing no, since we are doing promts. Prompts need to be delt with, and what you are saying you want to do, there is already 1 prompt running when you want to excecute another.
Hopefully I'm wrong.
However you can have multiple promts succeding each other.
For ex(biased info), like Hatchfaces crosshatching. By dropdownlist user selects YES or NO for crosshatching and click OK on the inputbox, who closes.
IF you clicked YES for "crosshatching", another different prompt pops up.
Stuff like that. You can have a look at the code. TIG helped me with that, so it should be "OK" on that part..