Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged, TextBox2.TextChanged
Dim n As Decimal, p As Decimal
If Decimal.TryParse(TextBox1.Text, n) AndAlso Decimal.TryParse(TextBox2.Text.Replace("%", ""), p) Then
TextBox3.Text = Math.Round(n * (p / 100) / 10000) * 10000
Else
TextBox3.Text = ""
End If
End Sub