Unfortunately it can't handle changing column widths at the moment, and probably won't in the future. This package is just meant for rapid prototyping mostly. Once you need more customized markup, it's better to just do it by hand.
There's no real automatic way to do it, but you can use BootForms to create individual buttons manually, like so:
Hi there, i have some questions:
1 can i custon two or more div width in the same form ? first
sorry for my poor english ,Thanks!!!