VBSの質問です

こういう事でしょうか。

Option Explicit

Const sText = "<meta http-equiv=""Content-Type"" content=""text/html;>"
Const rText = "<meta http-equiv=""Content-Type"" content=""text/html"" name=""robots"" content=""noindex,nofollow""> "

Dim fso
Set fso = CreateObject("Scripting.FileSystemObject")

Dim htmlFile
Dim htmlText
Dim folder
For Each folder In fso.GetFile(WScript.ScriptFullName).ParentFolder.SubFolders
    For Each htmlFile In folder.Files
        If fso.GetExtensionName( htmlFile.Name ) = "html" Then
            htmlText = fso.OpenTextFile( htmlFile.Path ).ReadAll()
            fso.CreateTextFile(htmlFile.Path,True).Write Replace(htmlText,sText,rText)
        End If
    Next
Next