How to use data from different callback in another callback in a GUI?

I Have this problem where i obtain a file name in a callback for a button, however i still need that filename at the click of another button. How do i do this.

handles.filename = uigetfile('*.txt');
filename = handles.filename;
guidata(hObject,handles);

and to get the data i used

get(handles.filename)

as well as

filename = guidata(hObject,handles.filename)

[Dennis]

to retrieve your filename try:

handles=guidata(hObject);
filename=handles.filename;

[Ahmed Emam]

thank you!