Set or update extra comment line ea - linear address n - number of additional line (0..MAX_ITEM_LINES) line - the line to display IDA displays additional lines from number 0 up to the first unexisting additional line. So, if you specify additional line #150 and there is no additional line #149, your line will not be displayed. MAX_ITEM_LINES is defined in IDA.CFG To set anterior line #n use (E_PREV + n) To set posterior line #n use (E_NEXT + n)void update_extra_cmt(long ea, long n, string line);