I have written a procedure "toto" that has no arguments, but 4 keywords. My problem is if I call the procedure with one or more arguments it tells me: "TOTO: Incorrect number of arguments." Instead I would like an error message telling me what is the usage of the procedure, something like: "toto, car=car, bus=bus, train=train, boat=boat" So I added at the beginning of my procedure the following: IF N_PARAMS() NE 0 THEN PRINT, "toto, car=car, bus=bus, train=train, boat=boat" However, because I called the procedure with too many arguments, IDL never enters inside the procedure, and always returns with the insignificant error message: "TOTO: Incorrect number of arguments." Does anyone knows how to avoid this error message and print something else when we call a procedure with too many arguments ? Many thanks in advance EA