gistfile1.vb

Public Class Form1
    
    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        If TextBox1.Text = "A" Then
            Dim arr As String() = New String() {"A", "B", "C"}
            Randomize()
            TextBox2.Text = arr(Math.Floor((3) * Rnd()))
        End If
        If TextBox1.Text = "B" Then
            Dim arr As String() = New String() {"A", "B", "C"}
            Randomize()
            TextBox2.Text = arr(Math.Floor((3) * Rnd()))
        End If
        If TextBox1.Text = "C" Then
            Dim arr As String() = New String() {"A", "B", "C"}
            Randomize()
            TextBox2.Text = arr(Math.Floor((3) * Rnd()))
        End If
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim nr As Integer

        Randomize()

        nr = CInt(Rnd() * 2) + 1
        If nr = 1 Then
            TextBox1.Text = "A"
        End If
        If nr = 2 Then
            TextBox1.Text = "B"
        End If
        If nr = 3 Then
            TextBox1.Text = "C"
        End If
    End Sub

    Private Sub TextBox2_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox2.TextChanged
        If TextBox1.Text = "A" And TextBox2.Text = "A" Then
            TextBox3.Text = "A1"
        End If
        If TextBox1.Text = "A" And TextBox2.Text = "B" Then
            TextBox3.Text = "A2"
        End If
        If TextBox1.Text = "A" And TextBox2.Text = "C" Then
            TextBox3.Text = "A3"
        End If
        If TextBox1.Text = "B" And TextBox2.Text = "A" Then
            TextBox3.Text = "B1"
        End If
        If TextBox1.Text = "B" And TextBox2.Text = "B" Then
            TextBox3.Text = "B2"
        End If
        If TextBox1.Text = "B" And TextBox2.Text = "C" Then
            TextBox3.Text = "B3"
        End If
        If TextBox1.Text = "C" And TextBox2.Text = "A" Then
            TextBox3.Text = "C1"
        End If
        If TextBox1.Text = "C" And TextBox2.Text = "B" Then
            TextBox3.Text = "C2"
        End If
        If TextBox1.Text = "C" And TextBox2.Text = "C" Then
            TextBox3.Text = "C3"
        End If
     End Sub
End Class