It looks like you need to handle the ItemSend event of the Application class which is fired whenever an Microsoft Outlook item is sent, either by the user through an Inspector (before the inspector is closed, but after the user clicks the Send button) or when the Send method for an Outlook item, such as MailItem, is used in a program. Be aware, the Cancel parameter passed to the event handler allows to cancel the action. If the event procedure sets this argument to true, the send action is not completed and the inspector is left open.
Public WithEvents myOlApp As Outlook.Application
Public Sub Initialize_handler()
Set myOlApp = Outlook.Application
End Sub
Private Sub myOlApp_ItemSend(ByVal Item As Object, Cancel As Boolean)
Dim prompt As String
prompt = "Are you sure you want to send " & Item.Subject & "?"
If MsgBox(prompt, vbYesNo + vbQuestion, "Sample") = vbNo Then
Cancel = True
End If
End Sub
In the code you can check out whatever you need - the Subject, Body or HTMLBody values.