|Figured it out on my own. Things to be asked or answered.
1) My application is 32 bit.
2) I have MDAC 64 bit on my windows 64bit OS.
3) When the CDatabase OpenEx executes with connection string i mentioned in my above code, it checks in ODBC32.exe in which the required driver (xlsx) is not available.
4) We must have to install the MDAC 32 bit and the required driver to read the xlsx file is will be available.
Hope this answer will be helpful to others in future and thought of writing my analysis.
Questioning is an Art and Answering will be done by only an Artist.