/* isdsn Daniel Brockman 110921 Test for the existence of dataset */
         %macro isdsn(dsn) ;
         /* = 1 if dataset &dsn exists
         /* = 0 otherwise
         /* dsn = library.name of a dataset 
         /* Example:
         /*   %if (1=%isdsn(work.yayb)) %then %do;
         /*        data work.roscoe ;
         /*          set work.yayb ;
         /*          if (note_dt>'31-Dec-2009'd) ;
         /*        run;
         /*   %end;
         /* */
         %if %sysfunc(exist(&dsn)) %then %let yesno=1 ;
		 %else %let yesno=0 ;
		 &yesno 
         %mend isdsn;