byte offset to pointer (C/C++)

I had the same question as this guy. I need to add some byte offset to a variable of struct something dataypes.

struct something data, *ptr.
char *helper;

ptr= &data;
helper= ptr;

&helper +offset ; // these two will do the same:
& helper[offset] ; // advances the helper by offset byte
*ptr + 1 will advance by the whole sizeof(struct someting)