Note: There are no forms in matlab, only figures.
Probably the simplest to get the controls of the figure is to retrieve the content of the Children property of the figure. Note however that it will return not only uicontrol, but uipanels, axes, etc.
fighandle.Children
Another option is to use findobj:
findobj(fighandle, 'Type', 'uicontrol')
Finally, there's findall which will return the whole hierarchy content, including hidden handles
findall(fighandle.Children)
