Look at Mark to Market from Tairox, at the bottom of this link:
http://www.tairox.com/customizations-for-sage-300-erp-accpac.html

Another option is to track it in the GL using a GL account segment for fund (or whatever you want to call it) and quantities. This obviously depends on the volumes you're dealing with, but for smaller operations I've done this.

There is also Ledger Manager from Dingosoft which gives you a full sub-ledger for any G/L asset or liability account. Basically similar to 49153's option of tracking it in the G/L, but Ledger Manager gives you sub-accounts to the G/L account which can be used for any purpose and full batch processing of payments, receipts, adjustments and transfers plus all the standard Sage 300 sub-module functionality and more. It doesn't have specific portfolio management functionality though, but does track quantities as well as amounts in transactions and balances. You can possibly use VBA to add the additional functionality you need. If you have investors, it's really good at tracking investor accounts in any sort of pooled fund. http://www.dingosoft.co/ledger-manager.html Actually, whenever you hear someone mention "doing it in the G/L", it's probably a job for Ledger Manager.