How to include a Group Plan DBA in the Basis of Calculation for an Employee Level DBA.

I am looking for a solution to this problem:

An employee has 401k set up at the Employee DBA level, which includes the DBA for the basis of calculation.

Because of a Davis Bacon job,  the employee may be eligible for a cash benefit, which is set up at the Group Plan DBA level.   That cash benefit should be included in the Basis of Calculation for the 401k.

The employee does not always work on the Davis Bacon job, so the cash benefit cannot be set up on the Employee DBA level.

Because of the hierarchy in which DBAs are calculated,  the Group Plan cash benefit is never included in the Employee's Basis of Calcullation for 401k.  We have tried adding the Basis of calculation DBA to the Group Plan, but that does not force a 'recacluation ' of the DBA.