The system allows you to specify the withdrawal order priority for all of the investment assets entered. To customize the withdrawal order browse to the Worksheets - Client Data - Assets & Liabilities tab and click on the Withdrawal Order button at the bottom of the page. This will open the pop up shown below. From here you can arrange the accounts in the order you wish to have them drawn down via the arrow icons.
Tip: Updated tax rules and regulations are built into the system. In addition, distributions are always going to draw, first, from any interest gained. Then it will draw from principal. If you set custom distribution schedules, then the system will start drawing from principal first, instead.