Possible to reopen a closed filestream?

Is it possible to reopen filestream object after it has been closed? What I am trying to do is combine to static text files together and write a few static lines in between. I am able to combine the two files in one new file but when I attempt to add a textwriter stream in between to write out my dynamic lines I get the error:

"The process cannot access the file "path to file" because it is being used by another process."

If I try to close the filestream before using the textwriter I am access the new files filestream to complete the combination of the two files receiving the error:

"Cannot access a closed file. "

Here is my existing code, hacked apart as it may be, for a better understanding of what I am trying to do:

=====================================================================
        Dim fn1 As String = "c:\temp\ini_files\ini_part_1.txt"
        Dim fn2 As String = "c:\temp\ini_files\ini_part_2.txt"
        Dim fn3 As String = "c:\temp\ini_files\ini_part_3.txt"

        Dim f1 As New FileStream(fn1, FileMode.Open, FileAccess.Read, FileShare.Read)
        Dim f2 As New FileStream(fn2, FileMode.Open, FileAccess.Read, FileShare.Read)
        Dim f3 As New FileStream(fn3, FileMode.Create, FileAccess.Write, FileShare.Read)

        ' Create a reader that can read bytes from the FileStream.
        Dim sr1 As New BinaryReader(f1)
        ' While not at the end of the file, read lines from the file.
        While sr1.PeekChar() > -1
            Dim input As Byte = sr1.ReadByte()
            f3.WriteByte(CType(input, Byte))
        End While
        sr1.Close()
        f3.Close()

       'Call function to write out dynamic content
        MyTools.WriteDynamicInfo(Session("strField1"), Session("strField2"))

        ' Create a reader that can read bytes from the FileStream.
        Dim sr2 As New BinaryReader(f2)
        ' While not at the end of the file, read lines from the file.
        While sr2.PeekChar() > -1
            Dim input As Byte = sr2.ReadByte()
            f3.WriteByte(CType(input, Byte))
        End While
        sr2.Close()

        f1.Close()
        f2.Close()
        f3.Close()
=====================================================================

Any suggestions on a more efficient approach to this procedure?

Thanks