Option Explicit

 Function TextFile_PullData() As String
'Graham Mayor - https://www.gmayor.com - Last updated - 23 Nov 2018 

 'PURPOSE: Send All Data From Text File To A String Variable
Dim TextFile As Integer
Dim FilePath As String
Dim FileContent As String
Dim fso As Object
    'File Path of Text File
    FilePath = Environ("USERPROFILE") & "\Temp\VFile.txt"
    'or for the User Temp folder
    'FilePath = Environ("TEMP") & "\VFile.txt"
    'However these are not the same folder

    Set fso = CreateObject("Scripting.FileSystemObject")
    If fso.FileExists(FilePath) Then
        'Determine the next file number available for use by the FileOpen function
        TextFile = FreeFile
        'Open the text file
        Open FilePath For Input As TextFile
        'Store file content inside a variable
        FileContent = Input(LOF(TextFile), TextFile)
        'Close Text File
        Close TextFile
        'Report Out Text File Contents
        TextFile_PullData = FileContent
    Else
        TextFile_PullData = ""
        Beep
        MsgBox FilePath & vbCr & " is not available"
    End If
    Set fso = Nothing
End Function

'Second part it takes the Information and adds it to this script in the TextFile_PullData

Sub UpdateSubject()
Dim SaveCode As String
Dim KeyWord As String
Dim objItem As MailItem

    KeyWord = "TSD"
    SaveCode = TextFile_PullData
    If SaveCode = "" Then Exit Sub
    Set objItem = GetCurrentItem()
    objItem.Subject = "[" + KeyWord + "=" + SaveCode + "] " + objItem.Subject
    Set objItem = Nothing
End Sub

Function GetCurrentItem() As Object
Dim objApp As Outlook.Application

    Set objApp = Application
    On Error Resume Next
    Select Case TypeName(objApp.ActiveWindow)
        Case "Explorer"
            Set GetCurrentItem = objApp.ActiveExplorer.Selection.Item(1)
        Case "Inspector"
            Set GetCurrentItem = objApp.ActiveInspector.currentItem
    End Select

    Set objApp = Nothing
End Function