But I only use assembly language.
That does in no way make it impossible to createe a struct.

structx ds 12
$set first_word_offset 0
$set first byte_offset 2
...

in the subroutine

.. assuming all is in (i)data
.. assuming the struct pointer is passed in R7
you could
mov r0,r7
add r0,#first byte_offset
mov r4,@r0

Erik