automatically left-aligning custom dynamics

[james]

I don't really understand it, but I can modify the examples of how to create 
custom dynamics to get what I want.
I have a document with several examples like:
rinforzamf = #(
   make-dynamic-script (
      markup #:line (
      #:left-align
      #:normal-text
      #:whiteout
      #:italic "rinforza"
      #:hspace 0
      #:whiteout
      #:dynamic "mf"
      )
  )
)
And a macro that left-aligns it:
leftalign = { \once \override Dynamics.DynamicText #'self-alignment-X = #-1 }

Heretofore, I've just been manually adding the \leftalign before the 
\rinforzamf (for example). Is there a way to get both of these in one command?

TIA,

James