Handling Events for Excel in navision from asp.net using webservice


I am working with .Net application that codeunits of navision through webservices, From .net application i upload an excel file and read the sheetnames using the codeunit,for that i use the ExcelBuffer table and SelectSheetNames function ,at that time i can’t create the excel ,gets the Excel not found error.,ie CREATE(XlApp,TRUE,TRUE) is not working .

Pls give me a valuable solution