INSTR            Find substring                               Macro Directive

  name INSTR [start_expr,] string1, string2     ; Ideal or MASM51 mode

    name is assigned a numeric value that is the position of the first
    instance of string2 in string1. If string2 does not appear anywhere
    within string1, a value of zero is returned. If you include
    start_expr, the search begins at the start_expr character.

    The first character of a string is one (1).