Hi Andy,
My apologies, there are a few more steps than I may have indicated. The button is only one part of it. You'll need to slightly alter the CRM_EditDocumentLink screen. The CRM_EditDocumentLink screen does grab all of the Shared Results and puts them on screen. There are however hidden actions that reset fields, then enter the correct information. You'll need to add the same actions for your new Purchase Order field.
I wonder if you're perhaps missing the new purchase order fields and the subsequent action to enter a value in the dropdown? You may also need to add the fields to any grids that are used also. Something else I thought of too, are you sure the edited CRM_EditDocumentLink screen is being called? You might need to change the Show Screen in Popup actions to show your edited screens.
To check which screen is being called in the popup, you can go through the process and right click the screen and click Customize. If the stock screen is being called, you'll only have the option to copy the screen.
- Adam