Row Level Security question

Sorry, FrankAT but that doesn't help. 

I am well versed in Dynamic Row Level Security in Power BI. I have it configured in many models, inclouding this one.

Perhaps a drawing or two will help explain my goal.
As stated before, any one user may be listed in the [Primary] field and/or the [Secondary] field. There is a Role defined for each of these two cases. Some users are listed a MEMBERS in both Roles. So a User may have access to see data as represneted by the following Venn diagram, where one circle represents those Clients where he/she is listed in the [Primary] column, and the other circle represents those clients where he/she is listed in the [Secondary] column. The FULL list of Clients that he/she will see is the COMBINATION of BOTH blue circles.

BUT, what I WANT is to have a way to filter the data for ALL users so that they only see Clients where they are listed in the [Primary] column, as represneted by the one colored circle below. It would be a SUBSET of all the data to which they have access.

IF I could use the USERNAME() or USERPRINCIPALNAME() function in a Calculated Column, this would be a non-issue. But I can't, so I'm asking the community if anyone has encountered and solved this.

Thanks.