In order to perform the crack / recovery, we are going to use a small utility called xlcrack, xlcrack recovers lost or forgotten passwords from XLS files such as those created by Microsoft Excel. Some newer XLS files are not suitable for password recovery using this software.
kartook@Nilas:~$sudo apt-get install libgsf-1-dev
Download and compile xlcrack
kartook@Nilas:~$tar zxvf xlcrack-1.2.tar.gz
How to Crack / Recover A Password From a XLS-file