Markup question

[Alexandre Beneteau]

Hello,

I'm presently writing an orchestral score an have a question about \markup :

I have to instruct 1st violins to put the mute several bars before they 
have to play.
I've tried to attach a markup to a R2., but it does not work (why ?), 
attach a markup to r2. works...

But I'm wondering if I have the good approach ? Is it possible to attach 
a markup to a Staff (I guess no... but ?)

Thanks in advance,

        Alex.