Maarten - is the function Tbrk_Callback a callback for the text field Tbrk, or is it for the push button? If it is the former, then you may want to reconsider putting this functionality in the push button callback - let it grab all data from the five fields, save them to the parameters file, and then run the code. Something like the following (note that some of the tags/names of the widgets will be different from yours, but the idea is the same)
function calcTbkrthPushbutton_Callback(hObject, eventdata, handles)
% get the data from the five widgets via the handles object
Tbrk = str2num(get(handles.Tbrk,'String'));
Tc = str2num(get(handles.Tc,'String'));
f = str2num(get(handles.f,'String'));
cv = str2num(get(handles.cv,'String'));
Wrel = str2num(get(handles.Wrel,'String'));
% save the parameters to file
save('parameters.mat','Tbrk','Tc','f','cv','Wrel');
% do other stuff
So the above will save the five parameters to a mat file which may not be what you intended since you say that you run this m-file, and you can't "run" a file of this type (the MATLAB binary formatted file). You can load the parameters from this file. Is that what you meant?
