How do you record 529 Plan funds?

[Geoff Catlin]

Hi,

I'd like to track a 529 College Savings Plan account and I'm having 
trouble recording stock/fund purchases. I've set up some accounts:

Assets
  529 Plans
    Name of Plan Here
      Cash
      Funds

I added transactions to transfer money into the Cash account from 
Equity:Opening Balances, but I'm stumped on how to record an actual fund 
purchase. The fund in question is "Vanguard Age-Based Option: Aggressive 
Track: Aggressive Growth Portfolio", it's particular to the 529 Plan and 
is not publicly traded. How does one record this type of transaction? Is 
it possible to add generic securities? Is there a better approach?

Thanks,

-Geoff