Extract_Script.vbs

Const FileFormat = 0 ' -2 - System default, -1 - Unicode, 0 - ASCII

strCurDir = CreateObject("Scripting.FileSystemObject").GetParentFolderName(WScript.ScriptFullName) & "\"
strPath = strCurDir & "child.vbs"
strFnName = "ChildScript"

WriteTextFile split(split(ReadTextFile(WScript.ScriptFullName, FileFormat), "Function " & strFnName & "()" & vbCrLf)(1), "End Function")(0), strPath, FileFormat

Function ChildScript()
    MsgBox "Extracted Child Script"
End Function

Function ReadTextFile(strPath, lngFormat)
    ' lngFormat -2 - System default, -1 - Unicode, 0 - ASCII
    With CreateObject("Scripting.FileSystemObject").OpenTextFile(strPath, 1, False, lngFormat)
        ReadTextFile = ""
        If Not .AtEndOfStream Then ReadTextFile = .ReadAll
        .Close
    End With
End Function

Sub WriteTextFile(strContent, strPath, lngFormat)
    ' lngFormat -2 - System default, -1 - Unicode, 0 - ASCII
    With CreateObject("Scripting.FileSystemObject").OpenTextFile(strPath, 2, True, lngFormat)
        .Write (strContent)
        .Close
    End With
End Sub