Changing sender email address in mailmerge for outlook

I need to send invitation to a list of recipient under my boss'es email, whom i got access as 'delegate'
i tried using VBA to change the sender address when the emails are in outlook 'outbox' , however, I faced <run-time error 438: object doesn't support this property or method>
below is the code used, can any one help to see where has gone wrong and help me fix it, please?

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thanks a lot

You didn't post your code, however, the following should change the sending account to then named account of ALL the mail items in the default outbox

Code:

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Sub ChangeAccount()Dim oMail As MailItem
Dim oAccount As Account
Dim i As Integer
Const strAcc As String = "display name of account"
    For Each oAccount In Application.Session.Accounts
        If oAccount.DisplayName = strAcc Then
            For i = Session.GetDefaultFolder(olFolderOutbox).Items.Count To 1 Step -1
                Set oMail = Session.GetDefaultFolder(olFolderOutbox).Items(i)
                With oMail
                    .SendUsingAccount = oAccount
                    .Send
                End With
            Next i
            Exit For
        End If
    Next
    Set oAccount = Nothing
    Set oMail = Nothing
lbl_Exit:
    Exit Sub
End Sub

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Or you could use https://www.gmayor.com/ManyToOne.htm in one to one mode and merge to the account of your choice.

thanks gmayor for your help, i will try yours and let you know , below is the one i used (sorry i posted as picture, the forum said the content contain forbidden words, so i can't post as text)
Attachment 24577