Help with MATLAB GUI

I am trying to build a GUI that programmatically changes the state of a radiobutton when certain conditions are met. I am coding the following within the callback:

function radiobutton1_Callback(hObject, eventdata, handles)
LPpumpHandle = findobj(gcbf, 'Tag','radiobutton1');
set(LPpumpHandle,'Value',1);

For some reason this will not work. Once you physically click on the radiobutton and the correct state is achieved it will not change but it will not just work automatically.

Also, is there a way to disable the mouse click function of the radiobutton and only allow it to work programmatically?

Help!