VB,Net, fast updating on textbox

Hi Experts
VB.Net 4
I have a queue to which I am adding +- 5000 strings on a separate thread
To Speed things up, while these strings are being added, I am taking the strings from the queue and adding them to a textbox, fired from a timer on the main thread.

If I use -
        If SelectedFilesQueue.Count <> 0 Then
            TextBox1.AppendText(SelectedFilesQueue.Dequeue.ToString & vbCrLf)
        End if
It works well but is VERY slow to complete

If I use -
          While SelectedFilesQueue.Count <> 0
            TextBox1.AppendText(SelectedFilesQueue.Dequeue.ToString & vbCrLf)
        End While
This is fast, takes a quarter of the time, but it freezes my GUI.

If I try and add the second example to a separate thread,  I still have the problem of updating the GUI from that thread
Anyone know how to keep the speed but stop the GUI from freezing?
Thanks in advance