This is usually not a process handled by stored procedures although it is not uncommon to have stored procedures move data between databases, there are better tools, like DTS.

Beyond what Larry has mentioned (using the sp_OA* stored procedures), you could experiment with using Dynamic SQL and OPENROWSET to access the Excel ODBC driver but you may not be able to create worksheets this way.

Why does this process have to be started by a stored procedure?

-Mike