Looking at EPiServer and ASP.NET postback eventing architecture and current implementation - I'm not sure that this could be easily achievable. We faced similar issue and this is something we ended up with:
a) Name each (hosting page and block) submit buttons
b) During postback hosting page and block will receive postback events
c) Check for incoming post values to determine either postback button was clicked in hosting page or in block itself.
d) Depending on value execute handler either in page ir in block
I have pagetype, which contains a block type that has a postback submit button. And the page type also has a submit button.
When I click the page type submit button, my block is also posted back. Is there a way to postback only to the pagetype controller.