MATLAB: How to save values entered in GUI text boxes as new defaults

gui

I adapted the two_axes example and got it to work for my curve fitting program. Now I want to add a Save as Default button so that the user can change the default values in the .fig file to the current values. It looks like guidata command might do that, but when I executed the program again I saw that it didn't change the .fig file. Is there a way to do this?
Thanks, Steve