On this line:
Code:
If objExcel.SaveWorksheet(Server.MapPath("foo.xls")) then
replace 'foo.xls' with any dynamic name you feel is necessary. You could even generate a GUID if using SQL Server like so:
Code:
Function CreateGUID()
    Dim cn
    Dim rs 

    Set cn = Server.CreateObject("ADODB.Connection")
    ' adjust the connection string if required
    cn.Open "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=sa;Data " _
        & "Source=(local)"
    Set rs = cn.Execute("SELECT NEWID()")
    If Not rs.EOF Then CreateGUID = rs(0)

    ' clean up 
    rs.Close
    cn.Close 
End Function