[daxb]

Check out the example WaitForPort (a command usually placed in Rexxc) in ARexxGuide: http://aminet.net/search?query=arexxguide2

Further I would first check the path of your command AmigaAMP with "IF EXISTS(<filespec>)" where <filespec> is the full path to AmigaAMP and if not exist exit the script with error message. More or less on top of your script.

   /**/
      /* @{" SHOW() " link ARx_Func2.ag/SHOW()} can be used to check for the existence of a port    */
   if ~show('P', 'VLT') then do
      address command    /* both RUN and WAITFORPORT are DOS commands.*/
      'run >nil: vlt:VLT'
         /*
            The loop below assures that the program will wait at least 50
            seconds for the port to open, but will exit as soon as the port
            is available.
         */
      do 5 while ~show('P', 'VLT')
         'waitforport VLT'
      end
      address           /* @{" toggle " link ARx_Instr.ag/ADDRESS 23} back to previous address           */
         /* The return code RC is set to 5 when WaitForPort times out  **
         ** before the port is available.                              */
      if rc = 5 then do
         say 'Unable to load VLT'
         exit
      end
   end