Relationship with foreign key on calculated field

[comment]

the DeliveryDate field is a calculated field that draws its value from the related Tasks table field "Report Date".

You couldn't mention this earlier? For example, when:

IIUC all the information required to determine whether to show a job in the portal or not is contained within the job record itself.

If so, it seems like you do need the Ugo method after all - but I suggest you first correct my file to reflect the real situation by adding the Tasks table and changing the ReportDate (wasn't it DeliveryDate earlier?) to the same calculation you are using (and any other changes that might be pertinent).

I wanted to be sure I understood your use of the Month(DeliveryDate)>6.

You do.