VB.NET Editting a variable

Hi all, I would like to thank all in advance for helping me. I am new to VB.NET so I need some help.

I have a code where I call a sub that appends text to a text box after which other codes also append text but once an instance has occurred I want one of the appended text by the sub to be updated but it must stay where it is, at the top of all text. Can someone show me a way of accomplishing this?

Basically...

Code
...
Public Sub CheckTitle()
If txtTextBox.Text = "" Then
txtTextBox.AppendText(trjTitle & Environment.NewLine & trjNumber & Environment.NewLine)
End If
End Sub
...
...
Code that appends text
...
Public Sub CheckTitle()
If txtTextBox.Text = "" Then
txtTextBox.AppendText(trjTitle & Environment.NewLine & trjNumber & Environment.NewLine)
End If
End Sub
...
...
etc.