Como pode exibir várias notificações, um após o outro

Estou um pouco perdida, eu não sei como exibir uma notificação após o outro. Vamos dizer, por exemplo, meu tempo é "23/11/2021 08:00" e eu quero criar um lembrete para "23/11/2021 09:30" a primeira vez que a notificação de pop-up, mas se eu criar outro lembrete para "23/11/2021 09:35" a notificação não aparecerá, a menos que eu fechar o programa após o primeiro lembrete de que a notificação foi apresentada e, por exemplo, se o usuário definir mais de 1 lembrete de que tem a mesma data e hora, em seguida, apenas 1 notificação deve ser exibido.

Obrigado.

Este é o meu formulário parece

Imports System.Data.OleDb

Public Class frmReminder

    Private CurrentReminderID As Integer = -1

    Private Sub frmReminder_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        BtnClear.PerformClick()
        Timer1.Enabled = True
        Timer2.Enabled = True
    End Sub

    Dim CurrentDateTime As Date
    Dim ReminderDateTime As Date

    Public Sub ShowNotification()
        Notification.ShowBalloonTip(1000, "Reminder", "Customer Order Due!", ToolTipIcon.None)
    End Sub

    Private Sub DateTimeVariable()
        CurrentDateTime = Date.Now
        CurrentDateTime = FormatDateTime(DateTime.Now, DateFormat.GeneralDate)
        ReminderDateTime = FormatDateTime(ReminderDateTime, DateFormat.GeneralDate)
        If CurrentDateTime = ReminderDateTime Then
            ShowNotification()

        Else
            If DbConnect() Then
                Dim SQLCmd As New OleDbCommand
                With SQLCmd
                    .Connection = cn
                    .CommandText = "SELECT ReminderDate FROM TblReminder"
                    Dim rs As OleDbDataReader = .ExecuteReader()
                        ReminderDateTime = (rs(0))
                End With
            End If
            cn.Close()
        End If
    End Sub

    Private Sub BtnClear_Click(sender As Object, e As EventArgs) Handles BtnClear.Click
        Label6.Text = ""
        TxtCustName.Text = ""
        TxtDeviceInfo.Text = ""
        TxtPrice.Text = ""
        TxtReminderDateTime.ResetText()
        CurrentReminderID = -1
    End Sub

    Private Sub BtnSetReminder_Click(sender As Object, e As EventArgs) Handles BtnSetReminder.Click

        If TxtCustName.Text.Length < 1 Then
            MessageBox.Show("Customer name is empty!" & vbCrLf, "Reminder", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            TxtCustName.Focus()

        ElseIf TxtDeviceInfo.Text.Length < 1 Then
            MessageBox.Show("Device Information is empty!" & vbCrLf, "Reminder", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            TxtDeviceInfo.Focus()

        ElseIf TxtPrice.Text.Length < 1 Then
            MessageBox.Show("No price entered!" & vbCrLf, "Reminder", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            TxtPrice.Focus()

        ElseIf DbConnect() Then
            Dim SQLCmd As New OleDbCommand
            If CurrentReminderID = -1 Then
                With SQLCmd
                    .Connection = cn
                    .CommandText = "Insert into TblReminder (CustomerName, DeviceInfo, RepairPrice, ReminderDate)"
                    .CommandText &= "Values (@CustomerName, @DeviceInfo, @RepairPrice, @ReminderDate)"
                    .Parameters.AddWithValue("@CustomerName", TxtCustName.Text)
                    .Parameters.AddWithValue("@DeviceInfo", TxtDeviceInfo.Text)
                    .Parameters.AddWithValue("@RepairPrice", TxtPrice.Text)
                    .Parameters.AddWithValue(" @ReminderDate", TxtReminderDateTime.Text)
                    .ExecuteNonQuery()

                    .CommandText = "Select @@Identity"
                    CurrentReminderID = .ExecuteScalar
                    Label6.Text = CurrentReminderID
                    'ShowNotification()
                End With
            End If
        End If
    End Sub

    Private Sub TxtCustName_KeyPress(sender As Object, e As KeyPressEventArgs) Handles TxtCustName.KeyPress
        If Not Char.IsLetter(e.KeyChar) Then 'Checks if key pressed isn't a digit
            If Asc(e.KeyChar) <> Keys.Back Then 'Checks the key pressed wasn't Backspace
                e.Handled = True 'It doesn't take any further action
            End If
        End If
    End Sub

    Private Sub TxtPrice_KeyPress(sender As Object, e As KeyPressEventArgs) Handles TxtPrice.KeyPress
        If Not Char.IsDigit(e.KeyChar) Then 'Checks if key pressed isn't a digit
            If Asc(e.KeyChar) <> Keys.Back Then 'Checks the key pressed wasn't Backspace
                e.Handled = True 'It doesn't take any further action
            End If
        End If
    End Sub

    Private Sub Notification_Click(sender As Object, e As EventArgs) Handles Notification.Click
        frmReminderInfo.Show()
    End Sub

    Private Sub Notification_BalloonTipClicked(sender As Object, e As EventArgs) Handles Notification.BalloonTipClicked
        frmReminderInfo.Show()
    End Sub

    Private Sub Timer2_Tick(sender As Object, e As EventArgs) Handles Timer2.Tick
        DateTimeVariable()
    End Sub

    Private Sub BtnOpenReminders_Click(sender As Object, e As EventArgs) Handles BtnOpenReminders.Click
        frmReminderInfo.Show()
    End Sub

    Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
        TxtCurrentDateTime.Text = Date.Now.ToString("dd/MM/yyyy      HH:mm")
    End Sub
End Class