how to block changing a quotation which is adopted by a purchase order?

Hi people,

I'm new to SAP and recently I was tasked to research on How to block changing a quotation which is being adopted by a purchase order. The process scenario should be:

- User goes to ME21N and create a purchase order that adopts a quotation.

- User goes to ME47 (maintain quotation) and enter the adopted quotation number

Expect: not allow user to change that adopted quotation.

I am working on an idea of using status profile, but everything is still hard to understand.

It's very appreciated if anyone can help me with this (step by step would be very nice).

Thanks in advance.