¿Cómo se puede mostrar varias notificaciones uno tras otro

Estoy un poco perdido no sé cómo mostrar una notificación después de la otra. Digamos, por ejemplo, mi tiempo actual es "23/11/2021 08:00" y quiero crear un recordatorio para "23/11/2021 09:30" la primera vez que la notificación emergente, pero si puedo crear otro recordatorio para "23/11/2021 09:35" la notificación no se mostrará a menos que se me cierra el programa después de la primera notificación de recordatorio ha sido exhibido y, por ejemplo, si el usuario establece más de 1 recordatorio de que tiene la misma fecha y hora, a continuación, sólo 1 notificación debe ser mostrado.

Gracias.

Esto es lo que mi forma 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