麗山50題之41

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If TextBox1.Text < 100 Then
            If TextBox2.Text < 100 Then
                TextBox3.Text = Val(TextBox1.Text) - Val(TextBox2.Text)
            End If
        End If
    End Sub
End Class