[color=darkblue]If[/color] IsNumeric(TextBox1.Value) And IsNumeric(TextBox2.Value) [color=darkblue]Then[/color]
TextBox3.Value = [color=darkblue]CSng[/color](TextBox1.Value) + [color=darkblue]CSng[/color](TextBox2.Value)
[color=darkblue]End[/color] [color=darkblue]If[/color]