Updating POHeader CommentText while PODetail/PORelease is added/updated

I have a BPM with a simple task to update the POHeader CommentText field when a new PO Line/Release is added.

I have a post-process UPDATE method which checks the conditions then set the ttPOHeader CommentText field. During testing the update event is forced by clicking save on the new line or adding a second line. The POHeader CommentText text can be seen in PO Entry> Header> Comment field.

However, if the screen is refreshed the text is erased. This tells me that the update is not taking the set value in the ttPOHeader temporary table.

I tried the pre-process UPDATE, with no luck either, instead the value does not even show in the PO Entry> Header> Comment field .

In the trace for adding the line, I can see that only the PODetails is being changed.

I did attempt the business object PO GetByID and Update method to update the Header but keep get the error business object reference not set to instance error message. After GetByID, I get the DS and set the ds.POheader.CommentText and then perform the update. The error occurs during the update.

I am trying to avoid updating the POHeader table using LINQ. I am at a loss on what to try next.

Decided to use LINQ.