Is there a way to check if the user has changed the value of a textbox?

I try to acces a variable in one of my methods to compare against the value but I can not seem to be able to access it?

Double click your TextBox1 and you will get the "TextBox1_TextChanged" Event.
This Event can also be located at the very top of the code window in the right ComboBox once your TextBox1 is selected in the left ComboBox. View attached image.

Try this in a New Project with 1 TextBox and 1 Button.

Public Class Form1

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        Me.BackColor = Color.Orange
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Me.BackColor = Color.Empty
        TextBox1.Select()
    End Sub
End Class