function clbBtnMatrixFile

global MatrixFileName
global Matrix

[filename, pathname, filterindex] = uigetfile( ...
       {'*.txt;*.*','Matrix file (*.txt, *.*)'}, ...
        'Select a Matrix file', MatrixFileName);

if ~filterindex
    return
end    
    
if isstr(pathname) && isstr(filename)
   MatrixFileName = [pathname filename];   

   h=findobj('Tag','txtMatrixFileName');
   set(h,'String',MatrixFileName);

   %Read the file
   Matrix = load(MatrixFileName);
   
end   