function Application_MailMergeDataSourceLoad(Doc) {
    let strDSName
    let intDSLength
    let intDSStart
    let DSName

    //Extract from the Name property only the file name
    DSName = Doc.MailMerge.DataSource.Name
    intDSLength = DSName.length
    intDSStart = DSName.lastIndexOf("\\") + 1
    strDSName = DSName.slice(intDSStart, intDSLength)

    //Deliver a message to user when data source is loading
    MsgBox("Your data source, " + strDSName + ", is now loading.")
}