Auto allocation, append next row if not able to allocate quantity

Hi all and good day,

I'm currently doing supply and demand fulfillment allocation.
I'm having issue with the store on hand quantity distribution with customer order quantity.
I need help on the formula smart enough to skip to next row if the store on hand quantity not able to fulfill order quantity

In short,
If the store on hand quantity balance still able to allocate, allocate it
If not able to allocate, move to next row

I have performed auto sorting based on customer priority, ship month and dates hence (refer to the attachment), the row sequence are not allowed to change.

Appreciated fellow forumers help on this issue