Any way in allegro skill to get bBox of all selected objects. I goal is to get a bBox which includes all the selected items

I wrote a simple routine for this, code shown below:

procedure(GetSelbBox()
    let((bBox llx urx ury lly)
        foreach(obj
            axlGetSelSet()
            if(bBox then
                when((caar((obj->bBox)) < llx)
                    (llx = caar((obj->bBox)))
                )
                when((cadar((obj->bBox)) < lly)
                    (lly = cadar((obj->bBox)))
                )
                when((caadr((obj->bBox)) > urx)
                    (urx = caadr((obj->bBox)))
                )
                when((cadadr((obj->bBox)) > ury)
                    (ury = cadadr((obj->bBox)))
                )
            else
                (bbox = (obj->bbox))
                (llx = caar((obj->bBox)))
                (urx = caadr((obj->bBox)))
                (ury = cadadr((obj->bBox)))
                (lly = cadar((obj->bBox)))
            )
        )
        (bBox = list((llx:lly) (urx:ury)))
        bBox
    )
)

The code I posted yesterday wasn't exactly correct, please use the code below:

procedure(GetSelbBox()
let((bBox llx urx ury lly)
foreach(obj axlGetSelSet()
if(bBox then
when((car(car((obj->bBox))) < llx)
(llx = car(car((obj->bBox))))
)
when((cadr(car((obj->bBox))) < lly)
(lly = cadr(car((obj->bBox))))
)
when((car(cadr((obj->bBox))) > urx)
(urx = car(cadr((obj->bBox))))
)
when((cadr(cadr((obj->bBox))) > ury)
(ury = cadr(cadr((obj->bBox))))
)
else
(bBox = (obj->bBox))
(llx = car(car(bBox)))
(lly = cadr(car(bBox)))
(urx = car(cadr(bBox)))
(ury = cadr(cadr(bBox)))
)
)
list((llx:lly) (urx:ury))
)
)