Can't access Excel get error message: System.UnauthorizedAccessException: Retrieving the COM class factory for component with CLSID

I’m using Visual Studio 2005 to do the development.
I need ASP.NET to:
1. Take data from an SQL database.
2.  Put data into an Excel spreadsheet (that is already created).
3.  The Excel Spreadsheet then does some calculations.
4. ASP.NET saves and copies the spreadsheet with new name.

The only thing not working is putting data into the Excel Spreadsheet (that is already created). It works on the desktop but when I run it on the server I get the following error message:

File Creation failed. Reason is as follows System.UnauthorizedAccessException: Retrieving the COM class factory for component with CLSID {00024500-0000-0000-C000-000000000046} failed due to the following error: 80070005. at RecreateFTAccountingFilesResults.Page_Load(Object sender, EventArgs e) in C:\inetpub\wwwroot\FAS\FuelTickets\RecreateFTAccountingFilesResults.aspx.vb:line 218


'------------------------------------
'Produce a Excel spread sheet
'-----------------------------------
Dim dsExcel As DataSet = DGS.OTR.FAS.Business.TransactionFilesFactory.GetTransactionsForSpreadsheet("5650-Garage Services", Month, Year)
Dim Excelrow As DataRow
Dim i As Integer

Dim MyExcel As New Excel.Application
Dim oWorkbooks As Excel.Workbooks = MyExcel.Workbooks

It errors out on Dim MyExcel As New Excel.Application. Excel is on the server.  It appears to be a permssions problem.

I don’t like doing it this way but was directed to put Excel on the server.  I didn’t create this someone else did.  I was just assigned the task of making it work. Personaly I would like it to access Excel on the desk top.  

Can anyone tell me how to fix this problem or give me links to a site that will tell me how to fix this problem?  If it’s easyer to use Excel on the desk top I’d be happy to change it.  I just don’t know how to do it. Can someone tell me our give me some sites that have instructions.

Thank you for any help you can provide.