problem with linked lists

[Tristan M]

i think these are linked lists...
what i'm trying to do is create a linked list, like the mprog one but i keep 
getting errors when compiling, heres the code:

403        STEP_DATA *list;

453        list->next = pRoom->step.list;
454        pRoom->step[step].list = list;

in merc.h

     typedef struct step_data STEP_DATA;

struct step_data
{
       int vnum;
       int current;
       int step_type;
       STEP_DATA *next;
};



so i try and compile that and i get this:
olc_step.c: In function `stedit_addprog':
olc_step.c:453: array subscript is not an integer
olc_step.c:454: array subscript is not an integer


i thought i basically copied how progs worked...can anyone point me in the 
right direction?