Similar to individual elements, layers can also be assigned to individual reference priorities.
With the following VBA example, any of the references attached to the current model can have its priority changed.

Sub ReferencePriority()
Dim  OATT As  Attachment
Const  RefPriority = 5   'is a value from -5 to 5
For Each oAtt In ActiveModelReference.Attachments
    If UCase(oAtt.Name) Like "*" Then
        oAtt.DisplayPriority = RefPriority * 1000000
        oAtt.Rewrite
    End  If
Next

In this specific example, each reference whose name begins with "TEXT" is set to the highest priority, which is always on top.
The range is from -5 to 5, whereas the reference priority is given a weight of 1,000,000.
This has a reference priority that always takes precedence over default priority and high priority items.