Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles TextBox1.TextChanged
 
        If TextBox1.Text = "" Then
            TextBox6.Text = ""
        End If
 
        If TextBox1.Text > 0 And TextBox1.Text <= 60 Then
            TextBox6.Text = "DHTG-65"
        End If
 
        If TextBox1.Text > 60 And TextBox1.Text <= 300 Then
            TextBox6.Text = "DHTG-90"
        End If
 
    End Sub