Error on open Excel Sheet on Web Services

Hi,

I need to make an unattended export process that collects some data and put it in an excel sheet.
This process is now working but it takes some time to finish, so I decided to execute this action by a call to a codeunit that is published as WebService. This method give me the option to run tasks that will be executed by "other user".

I have other tasks working like this but now, I'm getting some problems with the export to excel process. ](*,)

The problem comes when my process opens excel sheet to modify. The WS is returning the error (attached). This error is telling me that the file can't be found.

1.- I've checked access to the file. 2.- Client and server are all in the same testing server. 3-. No other process of excel are running.

The part of code is:

[b]CreateExcel()[/b]
CREATE(Appl, FALSE, TRUE);
Appl.Visible(FALSE);
XBook := Appl.Workbooks._Open(FileName);

Thank you,