Change account determination for Project purchases

Hi,

Our Project purchases (services) and project stock consumption are hitting GBB-VBR where as business wants a different G/L for all project procurement (services) and project stock consumption. We are planning to change the configuration to hit GBB-ZBR (new account modification). We will make change at account assignment category P/Q and movement type level to hit GBB-ZBR instead of GBB-ZBR at the time of consumption

My question is - Is it advisable to change this in the middle of company business when so many PR-POs are open in system? What would be the impact of making this change which we need to take care of

Thanks