problem with accent placement

[Alex Jones]

I’m using the Script.priority-order to place an accidental above a trill 
ornament, but when combining with a note accent it creates an ordering property 
as per the documentation example.  However with the following snippet:

\version "2.18.0"

\relative c''' {
a2-> \trill

\once \override Script.script-priority = #-100
a2-> ^\trill^\markup { \sharp }
}


The first note places the accent adjacent to the note and the trill above 
(which is correct)

when adding the \sharp and getting it above the tr it swaps the accent and 
trill ornament creates this side-effect.

Is there a way to specify the order between the three expressive marks?

Thanks!!!

-akj