Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        TextBox2.Text = TextBox1.Text + 1
        TextBox3.Text = TextBox1.Text - 2
        TextBox4.Text = TextBox1.Text * 3
        TextBox5.Text = TextBox1.Text / 4
    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        If Not (IsNumeric(TextBox1.Text) Or TextBox1.Text = "") Then
            MsgBox("값을 입력하세요", vbExclamation, "알림")
        End If
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        TextBox1.Text = vbEmpty
        TextBox2.Text = vbEmpty
        TextBox3.Text = vbEmpty
        TextBox4.Text = vbEmpty
        TextBox5.Text = vbEmpty
    End Sub
End Class