Task: GUI enabling_disabling of controls
C#: using System; 
using System.ComponentModel; 
using System.Windows.Forms; 

class RosettaInteractionForm : Form
{    

    
    
    class NumberModel: INotifyPropertyChanged
    {
        
        public event PropertyChangedEventHandler PropertyChanged = delegate {};

        int _value;
        public int Value
        {
            get { return _value; }
            set 
            { 
                _value = value;
                
                PropertyChanged(this, new PropertyChangedEventArgs("Value"));
            }
        }
    }

    NumberModel model = new NumberModel{ Value = 0};
    
    RosettaInteractionForm()    
    {
        
        var tbNumber = new MaskedTextBox
                        { 
                            Mask="0000",            
                            ResetOnSpace = false,   
                            Dock = DockStyle.Top    
                        };
        
        tbNumber.DataBindings.Add("Text", model, "Value");
        var enabledIfZero = new Binding("Enabled", model, "Value");
        EnableControlWhen(tbNumber, value => value == 0);

        var btIncrement = new Button{Text = "Increment", Dock = DockStyle.Bottom};
        btIncrement.Click += delegate
                        {
                            model.Value++;
                        };
        EnableControlWhen(btIncrement, value => value < 10);
        var btDecrement = new Button{Text = "Decrement", Dock = DockStyle.Bottom};
        btDecrement.Click += delegate
                        {
                            model.Value--;
                        };
        EnableControlWhen(btDecrement, value => value > 0);
        Controls.Add(tbNumber);
        Controls.Add(btIncrement);
        Controls.Add(btDecrement);
    }

    
    void EnableControlWhen(Control ctrl, Func<int, bool> predicate)
    {
        
        var enabledBinding = new Binding("Enabled", model, "Value");
        
        enabledBinding.Format += (sender, args) =>
            {
                
                if (args.DesiredType != typeof(bool)) return;
                
                args.Value = predicate((int)args.Value);
            };
        
        ctrl.DataBindings.Add(enabledBinding);
    }

    static void Main()
    {
        Application.Run(new RosettaInteractionForm());
    }
}

VB: VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   2265
   ClientLeft      =   60
   ClientTop       =   600
   ClientWidth     =   2175
   LinkTopic       =   "Form1"
   ScaleHeight     =   2265
   ScaleWidth      =   2175
   StartUpPosition =   3  
   Begin VB.CommandButton cmdDec 
      Caption         =   "Decrement"
      Enabled         =   0   
      Height          =   495
      Left            =   120
      TabIndex        =   2
      Top             =   1680
      Width           =   1215
   End
   Begin VB.CommandButton cmdInc 
      Caption         =   "Increment"
      Height          =   495
      Left            =   120
      TabIndex        =   1
      Top             =   1080
      Width           =   1215
   End
   Begin VB.TextBox txtValue 
      Height          =   495
      Left            =   120
      TabIndex        =   0
      Text            =   "0"
      Top             =   240
      Width           =   1215
   End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False

Private Sub cmdDec_Click()
    If Val(txtValue.Text) > 0 Then txtValue.Text = Val(txtValue.Text) - 1
End Sub

Private Sub cmdInc_Click()
    If Val(txtValue.Text) < 10 Then txtValue.Text = Val(txtValue.Text) + 1
End Sub

Private Sub txtValue_Change()
    Select Case Val(txtValue.Text)
        Case Is < 0
            txtValue.Enabled = False
            cmdInc.Enabled = True
            cmdDec.Enabled = False
        Case Is > 9
            txtValue.Enabled = False
            cmdInc.Enabled = False
            cmdDec.Enabled = True
        Case 0
            txtValue.Enabled = True
            cmdInc.Enabled = True
            cmdDec.Enabled = False
        Case Else
            txtValue.Enabled = False
            cmdInc.Enabled = True
            cmdDec.Enabled = True
    End Select
End Sub