HI Manjiri,
Rather than write a custom action block, why not use standard functionality with MII and Plant Connectivity (PCo):
1. Deploy PCo on a Windows PC (or MII Server is Windows Server OS), and create an OleDB Source System and Agent instance that can be queried from an MII PCoQuery. You can directly read the Excel spreadsheet and the results will be returned in the standard MII Rowset XML schema.
This option also allows direct connectivity with an Excel file that is on a Windows network even if MII is running on a Non-Windows OS.
Regards, Steve