Something to try is to use the 'Find in Files' feature under Edit, search for the symbol in your project directory and search *.c;*.h. This will show all occurrences and allow you to easily access them. It also will show the entire line so look for places where the symbol does not show an 'extern' preface but has a type identifier in front. Of course you'll need to check if using a global symbol locally in which case it would be ok without extern. Example search for 'int a'
main.c (10) int a;
menu.c (20) extern int a;
crypt.c (5) int a; <- no extern suspect because declared in main.c
Hope this help,
John