You should be able to adapt this for your needs:
Dim objFSO
Set objFSO = CreateObject("Scripting.FileSystemObject")
Dim objTemplateTS
Const ForReading = 1
Set objTemplateTS = objFSO.OpenTextFile("C:\MyTemplate.txt", ForReading, False)
Dim strAllTemplateText
strAllTemplateText = objTemplateTS.ReadAll()
objTemplateTS.Close()
strAllTemplateText = Replace(strAllTemplateText, "<Placeholder_One>", "My First New Value")
strAllTemplateText = Replace(strAllTemplateText, "<Placeholder_Two>", "My Second New Value")
Dim objOutputTS
Const ForWriting = 2
Set objOutputTS = objFSO.OpenTextFile("C:\Output.txt", ForWriting, True)
objOutputTS.Write(strAllTemplateText)
objOutputTS.Close()