'У формы ставишь свойство
KeyPreview = True
'На событие KeyUp
Private Sub Form1_KeyUp(sender As Object, e As KeyEventArgs) Handles MyBase.KeyUp
Select Case e.KeyCode
Case Keys.D1, Keys.NumPad1
TextBox1.Text &= 1
Case Keys.D2, Keys.NumPad2
TextBox1.Text &= 2
'...'
Case Keys.Back
If TextBox1.Text.Length > 0 Then TextBox1.Text = TextBox1.Text.Substring(0, TextBox1.Text.Length - 1)
End Select
End Sub