geht so:

Sub Remove_Reminder()
 
Dim olApp As Object
Dim myNameSpace As Object
Dim myFolder As Object
Dim myAppointments As Object
Dim myAppointment As Object
 
Set olApp = CreateObject("Outlook.Application")
Set myNameSpace = olApp.GetNamespace("MAPI")
Set myFolder = myNameSpace.GetDefaultFolder(9)
Set myAppointments = myFolder.Items

For Each myAppointment In myAppointments
    If myAppointment.Start = dteZeit Then
        myAppointment.ReminderSet = False
        myAppointment.Save
    End If
Next

olApp.Quit

Set myAppointment = Nothing
Set myAppointments = Nothing
Set myFolder = Nothing
Set myNameSpace = Nothing
Set olApp = Nothing
 
End Sub