Why not to use a regular expressions?
Something like this:
Code:
preg_match_all ("/\<xls\:Instruction\>(.*)\<\/xls\:Instruction\>/U", $output, $match0);
print_r ($match0);
preg_match_all ('/\<xls\:distance value\=\"([0-9]+)\" uom\=\"YD\"\/\>/U', $output, $match1);
print_r ($match1);