Update Business Process Flow stage

Hello experts,

I have two entities custom1, custom2 with a 1_N relationship ,so my custom1 entity contains a grid of records of the custom2 entity.

I need to change the stage of BPF on my custom1 entity when "ALL" the linked records of the custom2 entity changed the status.

Can I achieve this using WF? or should i do some cusomizations?

Thank you in advance,