How do I dynamically update a listbox using SQL and VB and hidden textbox

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VB

SQL

ListBox

I haven't written code in quite a few years and I have been given a task at work to attempt at making a entry/exit logging program. I have to connect to a SQL database that contains names and badge numbers. The badge numbers are obtained through a magnetic swipe reader. I need to figure out how to read the card into the hidden textbox and then search the database and display the associated name on a monitor. This program also needs to remove the name if the card is swiped again. I also don't quite know how to check the listbox to determine if a name is already listed so that it can be removed. I don't expect someone to write the program for me, I'm just looking for a few pointers or some resources that might get me pointed in the right direction.

What I have tried:

I have been able to come up with code that will fill the listbox on load but I need it to be blank at load and only show names as the cards are swiped. I have tried a using WHERE within the SELECT statement but I don't know how to read the textbox and assign it to something that can be compared in the WHERE statement.

Imports System.Data.SqlClient

Public Class EmployeeList

    Public conn As SqlConnection = New SqlConnection("Server=;Database=;Trusted_Connection=True;")
    Public cmd As New SqlCommand
    Public da As New SqlDataAdapter
    Public ds As New DataSet



    Private Sub EmployeeList_Load(sender As Object, e As EventArgs) Handles MyBase.Load

        conn.Open()

        Me.TextBox1.Text = "@BadgeNum"
        With cmd

            .Connection = conn
            .CommandText = "SELECT LastName FROM EmployeeData2 WHERE BadgeNumber = @BadgeNum;"
        End With

        da.SelectCommand = cmd

        da.Fill(ds, "EmployeeData2")

        With ListBox1
            .DataSource = ds.Tables(0)
            .DisplayMember = "LastName"
        End With

        conn.Close()

    End Sub