mec123 - you can set default values in the OpeningFcn of your GUI. Just do
set(handles.checkbox8,'Value',1);
to set the checkbox as checked and
set(handles.checkbox8,'Value',0);
to set the checkbox as unchecked.
Also, there is no need to use global variables. If you want one callback to access the values of the other controls, then use the handles structure as
function pushbutton1_Callback(hObject, eventdata, handles)
if get(handles.checkbox7,'Value') == 0
% do action 1
end
if get(handles.checkbox8,'Value') == 0
% do action 1
end
