send automatic mails once a week VBA - excel

Question

I have the bellow code to send automatic mails when some elements of my database are about to end ( 2 months before the ending dates), however I want the mails to be send once a week is there possible ?
How can I do that ?
Thanks for your suggestions
Dim Desti As String, Objet As String, Corps As String, olApp As Object
Sub AlertesDatesFormations() ' Formations externes
Dim Sh As Worksheet, Chaine As String, Lig As Integer, Alerte
Set olApp = CreateObject("Outlook.application")
Lig = 15 ' car les dates de validité se trouvent en ligne 15
For Each Sh In ActiveWorkbook.Sheets
If Sh.Range("A10") = "Formation externe " Then 'Formation concernée
Col = 2 ' car la premiére date de validité en en colonne B
While Sh.Cells(Lig - 5, Col) <> "" ' on regarde toutes les formations dans la colonne A10 (15-5=10)
If Sh.Cells(Lig, Col) <> "" And Sh.Cells(Lig, Col) < Date + 60 Then ' si formation et date
' on enrichit la chaine avec nom-date-formation
Chaine = Chaine & Sh.Name & vbTab & " Date: " & Sh.Cells(Lig, Col) & " " & Sh.Cells(Lig - 1, Col) & vbCrLf
End If
Col = Col + 1
Wend
If Chaine <> "" Then Chaine = Chaine & vbCrLf
End If
Next Sh
If Chaine <> "" Then
'MsgBox(Chaine, , "Alertes sur les dates de validit?formations.")
' Alerte = MsgBox(Chaine, , "Alertes sur les dates de validitéformations.")
MsgBox Chaine, , "Alertes sur les dates de validité formations."
Desti = "annabelle.delecour#nexans.com"
Objet = "Alertes sur les dates de validité des Formations Externes "
Corps = "Bonjour, ce message est un mail automatique, il vous informe sur la fin de valdité des formations externes, Merci "
EnvoiMail Desti, Objet, Corps
End If
End Sub
Sub EnvoiMail(Desti As String, Objet As String, Corps As String)
Dim M As Object
Set M = olApp.CreateItem(olMailItem)
With M
.Subject = Objet
.Body = Corps
.Recipients.Add Desti
.cc = "pascal.deguines#nexans.com;nicolas.debeyer#nexans.com"
.send
End With
End Sub

Answer 1

You have a concept problem. A macro doesn't run programatically and run only if the excel is open.
The problem to solve is easy, create an automatic task in windows, this task only have to do is open your excel file, in your excel file in vba in the workbookopen event call your macro and then close your file.
STEPS
1.Modify your Excel // VBA thiswoorbook event open call your macro sendmail
2.Create an automatic task weekly in windows this task only have to open your excel file