Manoj - are you saving your variables to the handles structure? Because it is this structure that is passed to the different callbacks, and it can be used to manage your user-defined data.
For example, in your one_Callback do the following
function one_Callback(hObject, eventdata, handles)
% do stuff
% set fields within the handles structure
handles.levelLow = levelLow;
handles.levelHigh = levelHigh;
% save the structure
guidata(hObject,handles);
Do the same in your two_Callback
function two_Callback(hObject, eventdata, handles)
% do stuff
% set fields within the handles structure
handles.lowH = lowH;
handles.highH = highH;
% save the structure
guidata(hObject,handles);
Now, in your pushbutton_callback, you can reference these local variables through the handles structure
function pushbutton_callback(hObject, eventdata, handles)
limits=[handles.LowH, handles.HighH];
% etc.
