Anyone who has at least some basic knowledge of VBA can crack it in minutes (here's an example of the VBA code that easily cracks passwords in Excel 2010 and lower). In older versions (below Microsoft Excel 2010), it doesn't even matter how long and complex your password is.
Even when you protect your Excel worksheet with a password, that password is very easy to break. Why? Because Microsoft Excel uses a very simple encryption algorithm for worksheet protection.
It's is not actually intended to prevent people from accessing data in a password-protected worksheet. Worksheet protection in Excel is not a security feature. What you need to know about Excel worksheet protection
