courses to become a Company Secretary

That depend on the career you wish to pursue. If you aspire to become a CS. The company secretary is responsible for the efficient administration of a company, particularly with regard to ensuring compliance with statutory and regulatory requirements and for ensuring that decisions of the board of directors are implemented.
1. CA is a vital link between the company and its Board of Directors, shareholders, government and regulatory authorities.
2. A CS ensures that Board procedures are both followed and regularly reviewed and provides guidance to Chairman and the Directors on their responsibilities under various laws.
3. CS Commands high position in the value chain and acts as conscience seeker of the company.
If this is what you wish for yourself than you can pursue CS else their many option after B.com such as M.Com, MBA, etc.