How to Reference System Members in XPath

I have select all System Members when creating an entity called "Customer" . Can some one tell me how to reference them in a Xpath database retreive on Customer where it is = %CurrentUser%. I have tryed many combinations, one of which is [MyFirstModule.Customer/Owner = '[%CurrentUser%]']. I am new to Mendix so if possible please could you point me to a help section that I can look at.
2 answers

Xpath should be [id = $currentUser]


Instead of asking the "technical" question, provide us with the reasoning behind what you are trying ti accomplish ?

iow. paste in some screenshots of your domain model and explain what the bussiness logic is of what you are trying to do !