Checking File Size

I need to write a batch file that goes out, checks the size of a file (ie asjob.txt) and determines whether or not this is a 0k file or not, If the file is 0k it should goto the next check, if it is 1k or more it should execute a psservice/stop command.

I would appreciate if someone can give me a hand in checking the filesize and using it in either an if then goto command?