What i have understood from your question is you want to export the system fields to excel or text files?
You could do it with post reload trigger.
Create a pivot table with all sysyem field. Right click on sheet i.e. GUI and go to "New Sheet Object" --> "System Table". once you do this, write a macro to export this pivot table to desired loaction and map the macro to post reload trigger of Document Property.
Sample Macro to export the data to excel.
'on the place of "CH01" give your pivot table object id
set obj = ActiveDocument.GetSheetObject("CH01")
Hope this helps you.