SendMessageEx(); - What are the parenthesis inside?

I wanted to send a message to one of my custom cog (test.cog). Do the lines below accomplish this in a modification patch? (Assuming the test.cog and message "user0" in the cog exist)

   symbols
      cog         dest_cog=test.cog       local
      model      jerecModel=je.3do      local
      message  startup
   end

   code
      startup:
      SendMessageEx(dest_cog, user0, GetLocalPlayerThing(), jerecModel, 0, 0);
      return;
   end

Assuming the above SendMessageEx(); function had successfully arrived to another cog with following lines. Did the player model change to "je.3do"?

   symbols
      message   user0
   end

   code
      user0:
      SetThingModel(GetParam(0), GetParam(1));
      return;
   end