Hello Evryone

I have an Edit form that has two Richtextboxes:
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I would like to keep track of who makes the changes or edits the form, and I have the following code: and is working just fine:
Dim stamp As String = "Edited by " & LoginForm1.UsernameTextBox.Text & " on " & Date.Now.ToString
Me.RichTextBox1.AppendText(Environment.NewLine & stamp)
Me.RichTextBox2.AppendText(Environment.NewLine & stamp)
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The problem that I am having is that I would like to only add the tracking*log to the RichTextBox that I am modifying.
Right now if I edit RichTextBox1, it will add the tacking log, but is also adding the tracking log to the RichTextBox2, and I have not touched RichTextBox2,
How can I make it to work to only add the tacking log to the one that I am touching?
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Thanks for your help