1) IS the OP Wiccan? If not then the Rede doesn't apply at all.
2) There is NO LINE in the Rede that says "don't harm". It just tells you that you can go ahead if no harm is caused. I says nothing about what to do if harm IS caused. That's the lovely thing about the Rede, it gives the reader credit for a functioning brain.
3) Rede means "advice" not "law". So even if the spell DID contravene the Rede that doesn't really amount to anything.
I know some one who did this. It worked too, to my complete amazement.
The trick I was told is assembling the box in a dark place, under a cloth; then bury the box.
I'm not so keen on the second version, but the first makes good sense. I've used similar spells before to great effect. Some where very temporary (need to make it through dinner with out reaching across the table and throttling the idiot) and others were years in duration.