How to create a role who can't create change orders

Summary:

How to create a role who can't create change orders ?

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Hi,

I'm not sure i'm at the right place but I would like to prevent any users from creating change orders on a PO.

For this, I started creating a role 'GB - Buyer" for which I deleted the Function Security policy "Change Purchase Order".

This enabled me to have, on some PO's, the "edit" button greyed out. As you can see on the right of this screen, the user that has only GB Buyer role can't edit this PO when the Admin on the left can (as expected) :