i am getting errors when i run code in this way

Error using imwrite (line 459)
Can't open file "..\Dataset\Testing\stegoimage.bmp" for writing.
You may not have write permission.

Error in D:\ym phd work progress\paper 1
code\MR141022-Archana_Toolbox_V4.5CF\embeddedImg.p>embeddedImg (line 82)

Error in Main_Toolbox (line 25)
            embeddedImg(secMsg,dictionary,coverImg);

my code is

for (line 459)
% Verify that the file can be written to.
fid = fopen(filename, 'a');
if (fid == -1)
    error(message('MATLAB:imagesci:imwrite:fileOpen', filename));
else
    % File can be created.  Get full filename.
    filename = fopen(fid);
    fclose(fid);
end

*line 25*  

          case 3
              disp('Embedding');
              embeddedImg(secMsg,dictionary,coverImg);

line 81

imwrite(embmtx12,'..\Dataset\Testing\stegoimage.bmp');
figure,imshow(embmtx12),title('stegoimage');