UpDaTe ChIlD reCoRd WhEn PaReNt ReCoRd Is UpDaTeD

Hello guys

I have a requirement

Entity oppertunity is having 1:n relationship with Entity A and the oppertunity entity having subgrid of entity A

when status of oppertunity is updated i need to update child record associated with it

i want to achieve this in plugin

give me an idea how to make it

thanks in advance