File Renaming

I have had a go at using a package with a script to rename and move a file and it works well by using a script task in a package with source and destination variables. See script at bottom
But in my scenario the file thst comes in every day will have a slightly different name. It will be called "System_UT_INCR_BOOKINGHEADER_20080228000000.TXT"
On the 28th Feb. The date part of the title changes everyday.

SO i need to adjust my "Source" variable which is currently just a string with a value of "C:DatafilesimportsSystem_UT_INCR_BOOKINGHEADER_20080228000000.TXT" So it will only ever look for that exact file name



Imports System.IO
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()
Try
File.Move(Dts.Variables("Source").Value.ToString, Dts.Variables("Destination").Value.ToString)
Dts.Events.FireInformation(0, "", "File Moved Succesfully", "", 0, True)
Catch ex As Exception
Dts.Events.FireError(1, "", "Source file or destinations does not exist", "", 0)
End Try

Dts.TaskResult = Dts.Results.Success
End Sub

End Class