Next button press does not return a new value from mSQL

I am trying to draw random employees from a mSQL database with a button press any needed amount of times. The first button press returns a random employee with no issue but the second or any thereafter just return my exception errors. I know it has to something really simple I am missing and I an very new to programming with VB or anything for that matter. Below is the code I am trying to make function and any suggestions are very much appreciated.

Private Sub btnDrawEmployee_Click(sender As Object, e As EventArgs) Handles btnDrawEmployee.Click
            ' * Randomly draw a employee number from the database
    If txbSetSessionNumber.Text = "" Then
        ' * Do nothing
        lblEnterValidEmployeeID.Visible = True
        lblEnterValidEmployeeID.Text = "PLEASE ENTER/CHECK SWIPE SESSION NUMBER."
    Else
        Try
            sqlConn.Open()
            lblEnterValidEmployeeID.Visible = False
            Dim time = Date.Today
            Dim cmd As SqlCommand = New SqlCommand(("SELECT TOP 1 * FROM Swipe_Data WHERE Session =" + txbSetSessionNumber.Text + "AND Date =" + "'" + time + "'" + "AND Drawn IS null ORDER BY NewID()"), sqlConn)
            Dim da As SqlDataAdapter = New SqlDataAdapter(cmd)
            Dim dt As DataTable = New DataTable
            da.Fill(dt)
            dgvDrawnEmployee.DataSource = dt
            ' * Pull data from GridView to label
            lblEmployeeNumber.Text = dt.Rows(0)("EmpNumber").ToString.Trim
            lblEmployeeName.Text = dt.Rows(0)("EmpName").ToString.Trim
            lblEmployeeDepartment.Text = dt.Rows(0)("EmpDepartment").ToString.Trim
            lblDrawDate.Text = dt.Rows(0)("Date").ToString
            '
            'dt.Clear()
            'da = Nothing
            'dgvDrawnEmployee.DataSource = Nothing
            'dgvDrawnEmployee.Rows.Clear()
            'dgvDrawnEmployee.Refresh()
            ' * Mark employee as drawn
            drawnEmployee()
        Catch ex As Exception
            lblNoData1.Text = "No employees have been scanned/swiped in matching the session"
            lblNoData2.Text = "criteria entered above! Please enter a valid session number."
            lblNoData3.Text = "IT info - " + ex.Message
        End Try
    End If
End Sub