Export to Excel problem

I am using the following code of line to export the details into excel in my web application
testFileName = "Proposal" & id & ".xls
Response.AppendHeader("Content-Disposition", "attachment; filename=" & testFileName) .
The dialog to open /save excel is appearing in the application,
On click of Save no problem, but
On click of Open the file name contains Proposal2[1].xls, i am not sure why the [1] is getting appended to the file name.
How to prevent [1] getting appended to the file name.
 
Thanks,
Kaliprasad.
 
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