VBScript Replace specific value with regex and modify text file

I know there are a lot questions similar to this one but i couldn't find the right answer for me. I need to replace all phrases in xml file that starts and ends with % (e.g. %TEST% or %TEST-NEW% )

So far i have these tryouts: This was my test one that works in the console but has only 1 line of string

zone = "<test>%TEST%</test>"
MsgBox zone
'Setting the regex and cheking the matches
set regex = New RegExp
regex.IgnoreCase = True
regex.Global = True
regex.Pattern = "%.+%"
Set myMatches = regex.execute(zone)
For each myMatch in myMatches
Wscript.echo myMatch
result = Replace(zone,myMatch,"")
next
MsgBox result

but when i try to do the same from a file with this...

Dim objStream, strData, fields
Set objStream = CreateObject("ADODB.Stream")
objStream.CharSet = "utf-8"
objStream.Open
objStream.LoadFromFile("C:\test\test.xml")
strData = objStream.ReadText()
Wscript.echo strData

set regex = New RegExp
regex.IgnoreCase = True
regex.Global = True
regex.Pattern = "%.+%"
Set myMatches = regex.execute(strData)
For each myMatch in myMatches
Wscript.echo myMatch
result = Replace(strData,myMatch,"")
next
Wscript.echo result

...the first echo returns correctly the contains of the file and then the second echo in the loop echoes all the matches that i need to replace , but the last echo return the same result as the first (nothing is being replaced)

The xml looks like this (just for example):

<script>%TEST%</script>
<value>%VALUE%</value>
<test>%TEST%</test>

P.S. I need to loop through xml files in a specific folder and replace the phrase from above. Can anyone help?

The final script that works for me(big thanks to Tomalak):

Option Explicit

Dim path, doc, node, placeholder,srcFolder,FSO,FLD,fil

Set placeholder = New RegExp
placeholder.Pattern = "%[^%]+%"
placeholder.Global = True


srcFolder = "C:\test"
Set FSO = CreateObject("Scripting.FileSystemObject")
Set FLD = FSO.GetFolder(srcFolder)

For each fil In FLD.Files

    if LCase(FSO.GetExtensionName(fil.Name)) = "xml" Then

            path = "C:\test\" & fil.Name

            ' 1. parse the XML into a DOM
            Set doc = LoadXmlDoc(path)

            ' 2. select and modify DOM nodes
            For Each node In doc.selectNodes("//text()|//@*")
                node.nodeValue = SubstitutePlaceholders(node.nodeValue)
            Next

            ' 3. save modified DOM back to file
            doc.save path
    End If

Next            
' --------------------------------------------------------------------------

Function LoadXmlDoc(path)
    Set LoadXmlDoc = CreateObject("MSXML2.DomDocument.6.0")

    LoadXmlDoc.async = False
    LoadXmlDoc.load path
    If LoadXmlDoc.parseError.errorCode <> 0 Then
        WScript.Echo "Error in XML file."
        WScript.Echo LoadXmlDoc.parseError.reason
        WScript.Quit 1
    End If
End Function
' --------------------------------------------------------------------------

Function SubstitutePlaceholders(text)
    Dim match

    For Each match In placeholder.Execute(text)
        text = Replace(text, match, GetReplacement(match))
    Next

    SubstitutePlaceholders = text
End Function
' --------------------------------------------------------------------------

Function GetReplacement(placeholder)
    Select Case placeholder
        Case "%TEST%": GetReplacement = "new value"
        Case "%BLA%": GetReplacement = "other new value"
        Case Else: GetReplacement = placeholder
    End Select
End Function
' --------------------------------------------------------------------------