I'm not sure what you're looking for -- TCSTART (and TCEXIT) do not execute any batch files unless you add them yourself.
Or are you referring to starting TCC with a batch file argument, and you want to know the name of that batch file while you're still in TCSTART? If that's what you want, use %CMDCMDLINE (which returns the startup command line), and look for the second argument.
Thanks, Rex. Yes, it's the name of the file which will be executed, but I want to know what it is while still executing TCSTART. It isn't always the second argument, though, is it? There could be TCC startup switches. I was hoping for something I didn't have to parse.