[Aly El-Haddad]

كود :

Public Class Form1

    Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If Not Double.TryParse((TextBox1.Text & e.KeyChar), Nothing) Then
            e.Handled = True
        End If
    End Sub
End Class