[NTG-context] Stop with an error signal

Hi, I want to write a macro that checks for some settings and if the settings are wrong stop the current compilation and terminate with an error message. Right now I have \def\ERROR {\writeline \showmessage\??externalfilter??{forbidden}\getexternalfilterdirectory \batchmode \normalend} This prints the error message on the terminal and exits. However the exit status (the value of $?) is 0, if the tui file has changed the document is compiled a second time anyways. How can I force context (the macro package) to exit with a status of 1 so that context (the program) does not attempt a second compilation? Thanks. Aditya