Interpolate Vim function and shell command arguments

I wrote a small .applescript file that can restart Safari. I tried to hook it up to the vim BufWritePost event (so that Safari automatically reloads when the file is saved).

I posted this in my .vimrc:

function! SaveAndReloadSafari(delay) 
   " THIS IS WHERE MY PROBLEM IS>>>>>>>>>>>>>>> 
   !osascript ~/MySrc/applescript/reloadSafari.APPLESCRIPT a:delay
endfunction

if !exists("b:my_autocommands_loaded")
  let b:matts_autocommands_loaded = 1 

  au BufWritePost *.html,*\.css,*.js call SaveAndReloadSafari(0)
  au BufWritePost *.scss call SaveAndReloadSafari(2)
endif

      

        
        
        
      

    

As you can see, I want to add a 2 second delay after saving the .scss file (so that my SCSS files will automatically compile to CSS)

I have confirmed that the only drawback of the puzzle is my syntax for interpolating a: delay with a shell command. (Running the command without a parameter delay

works fine).

What's wrong with my syntax?