Budgeting asset transfers

[Steven Hood]

How would one go about setting up a budget for asset transfers such as
a 401(k) contribution or a 529 contribution?  I've been following an
envelope-style process similar to what's described at
http://allmybrain.com/2008/12/15/better-budgeting-with-gnucash/ for
income and expenses with great success.

I have a a Budget account at the top level with sub-accounts that
offset my Income and Expense accounts.  I know what I intend to
transfer (the budgeted value), but I'd like to be able to include that
in my Budget accounts so that the Budget account will zero out.  It
seems like I need to make it an Expense of some sort, but the
approaches I've tried so far haven't given the desired results.  My
typical paycheck transaction has a list of debits for Assets and
Expenses and a credit for Income.  Trying to have the Budget
transaction include the Asset account messes up the accuracy of Assets
and Liabilities, thus distorting my net worth picture.  I think the
problem comes from the fact that an asset transfer is really a net
zero transaction from the perspective of the accounting equation.

Any ideas?  Can I represent the transaction in some other way?

Thanks,
Steven