Equity in Blotter

Hi.

I am exploring blotter and find it very useful. However, I have a question
about the equity.

Let us say, I have a some code like this:

  addTxn(Portfolio = "p", Symbol = symbols, TxnDate =
as.Date(index(stockSymbol[i])), TxnQty = 13, TxnPrice = 1000, TxnFees = 0)

...
initAcct(name="a", portfolios="p", initEq=12000, currency="USD",
initDate=sDate)
updateAcct("a",Dates=interval)
updateEndEq("a",interval)
PortfReturns(Account="a",Dates=interval, Portfolios="p")


i.e, in the account, I start with an equity of $12000, but purchase shares
worth $13k. Ideally, such a transaction should be prevented because I don't
explicitly setup an account to borrow the 1k from. Second, the equity
calculations should take into account that the money is borrowed and should
keep track of it while calculating equity. Any thoughts on the right way to
handle it using blotter?