Hex Editor - Binary File Editing Software for Windows
Docs

$shift_by Directive

Syntax:

$shift_by(integer-expression);

This directive updates the current_offset. It may be used to have look ahead in a structure. integer-expression is evaluated at run-time and must be an integer value, which is added to current_offset upon directive execution.

struct A
{
    int skip_bytes;
    $shift_by(skip_bytes);
    int next_field;
};