don't know much about osX but for sure in windows you can create a .bat file using the text editor, just putting 'Render' command after 'Render' command - running the file will complete all the commands in the batch file you made... so if you can create something similar in osX and run it you should be ok.

oh wait but you can't do command line rendering on a mac, can you? ugh i guess i got nothin.