Using 'normalized' units generally helps to do this, but only if you do it for all components, panels and the main figure. This usually happens for you in a GUIDE-based GUI if you choose the 'Proportional' resize option from the relevant menu in GUIDE (I can't check at the moment exactly what the menu option is called, but there aren't many of them in GUIDE so it is easy to find).
That still isn't ideal as normalized units can cause some problems (such as a bug when you have nested panels causing components within these to disappear).
It also doesn't resize text as this has its own setting so you can get some odd looking UIs with extra big text when the UI components have shrunk for a smaller screen.
