Stock Depletion / Projected Stock

I want to create a measure that forecasts Inventory/Stock Depletion.

Arithmetically it should be: (Inventory+Inbound) - Projected Sales
In below screenshot (Total Stock Amount + PO Amount) - Projected Sales

Problem is that the data set I have, already has a value for future months which is 0. How do I prevent Power BI from using the inventory data value in the data set, and use the result of this measure for future months.

Any help will be highly appreciated.

Kind regards,

MightyMike 🙂