To use a path which contains spaces in a win32 command window, you have to surround the path in quotes. Otherwise the interpreter sees the first space delimited text as the command and each following delimited text as arguments to that command.

use strict;
use warnings;

my $app = '"C:\Program Files\Microsoft Office\Office\excel.exe"';

my $arg = '"C:\Documents and Settings\Administrator\My Documents\data\
+Excel\temp.xls"';

system("$app $arg");
[download]

Also, please remember to

use strict;
use warnings;
[download]

Update:
You'll need to do the same thing with your args. Updated code with a tested and working mini-script.