its all done in asm but whats allocated is not accessable to pbp directly

simple way , create a word var as an address register, and another as an index , pbp can run with them

and in asm you can transfer data to or from any location using the fsr , indirect address is address+offset

its most useful as a buffer,
but its way simpler to allocate a whatever size buffer you think you need in pbp the normal way unless dynamic allocation is your only option