use a VB Script to change the file name. I use the below script to do that exact same thing to an excel export from a OLE DB Source

Microsoft SQL Server Integration Services Script Task

' Write scripts using Microsoft Visual Basic

' The ScriptMain class is the entry point of the Script Task.

Imports System

Imports System.Data

Imports System.Math

Imports Microsoft.SqlServer.Dts.Runtime

Public Class ScriptMain

' The execution engine calls this method when the task executes.

' To access the object model, use the Dts object. Connections, variables, events,

' and logging features are available as static members of the Dts class.

' Before returning from this method, set the value of Dts.TaskResult to indicate success or failure.

'

' To open Code and Text Editor Help, press F1.

' To open Object Browser, press Ctrl+Alt+J.

Public Sub Main()

Dim mydate As Date

Dim ExportFileName As String

mydate = DateAdd(DateInterval.Day, -1, System.DateTime.Today)

ExportFileName = "c:\" + "T" + mydate.ToString("yyyyMMdd") + ".xls"

Dts.Variables("ExportFileName").Value = ExportFileName

Dts.TaskResult = Dts.Results.Success

End Sub

End Class