Automatic entries based on a current manual entry

[AC]

I know the subject is a bit confusing but there isn't much room.  I was
wondering if there is a way to have GC insert an entry into an account
automatically using data from a manual entry.  Specifically I want to
keep track of rewards points that accumulate every time I make a
payment.  The number of points is equal to the payment itself.  So if I
enter a transaction to pay an account from say my checking account, I
would like to automatically make a duplicate entry in the "reward points
account" to increase its balance.