OnPress Callback

[Wanngo]

hi everyone , i'm have problem with gui callback

pseudo code
void Ret_CallBack(Gwen::Controls::Base *p)
{
//some code
}

Gwen::Controls::Button *pButton = new Gwen::Controls::Button(pCanvas);
//pCanvas == SFML Window
pButton->SetText(L"CLICK ME!");
pButton->OnPress.Add(pCanvas,&_CallBack);

I'm not understand template to CallBack function

Someone can help me , upload own code /
not using UnitTest( with this classes)

sorry bad eng! :)