[Genius Live]

You can use something like this

كود :

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
        If ComboBox1.SelectedIndex = 0 Then
            TextBox1.Text = "3000"
        ElseIf ComboBox1.SelectedIndex = 1 Then
            TextBox1.Text = "2000"
        ElseIf ComboBox1.SelectedIndex = 2 Then
            TextBox1.Text = "1000"
        ElseIf ComboBox1.SelectedIndex = 3 Then
            TextBox1.Text = "750"
        ElseIf ComboBox1.SelectedIndex = 4 Then
            TextBox1.Text = "500"
        ElseIf ComboBox1.SelectedIndex = 5 Then
            TextBox1.Text = "300"
        End If
    End Sub