Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim VIPCustomers() As String = {"JOE", "JOHN"}
Dim PromotionItem() As String = {"A", "B", "C"}
Dim myProduct As String
Dim CustomerExist As Boolean
Dim ItemExist As Boolean
Dim num As Integer
myProduct = ListBox1.SelectedItem
CustomerExist = False
num = 0
Do While num < 4
If TextBox1.Text = VIPCustomers(num) Then
CustomerExist = True
End If
num = num + 1
Loop
If CustomerExist = True Then
TextBox3.Text = CInt(TextBox2.Text) * 0.9
Else
TextBox3.Text = CInt(TextBox2.Text) *10
