You can use dir to get a list of all of the files in a directory. It also allows you to specify the a string to match particular files, you could use '*.xml' to select only files with that extension: see the documentation for more info and examples. Also note that you should use fullfile to generate the full filepath string:
pth = uigetdir(...);
fnm = fullfile(pth, '*.xml');
S = dir(fnm);
Where S is a structure containing lots of useful info. You can get a cell array of the filenames like this:
C = {S.name};
