Solution was simple and enough elegant for me...
.
function pushbutton1_KeyPressFcn(hObject, eventdata, handles)
    key = get(gcf,'CurrentKey');
    if(strcmp (key , 'return'))
        pushbutton1_Callback(hObject, eventdata, handles)
    end
function pushbutton1_Callback(hObject, eventdata, handles)
    %code to be executed


