To control the button caption (text), you'll need to add a Data Types/Text element to the button and call it <Caption>. Passing some string to the <Caption> element will set/change it in the browser.
In the attached project you can see an example of this, as well as one possible implementation of a button creating an additional row with a button.
I suggest you import and run it, and if you need help figuring out the details, try using the trace facility, described @ http://www.tersus.com/#Id=46.
Of-course you're also welcome to post followup questions in the forum.
For best results, use the Firefox browser..