Just such a spell was already discussed at some length in another thread a couple months back...
Here it is...
https://forum.atlas-games.com/t/new-item-for-moderation/1883/1
That said, the spell you have submitted above does not actually conform to the RAW. To create treated AND processed Herbam products (not simply usable finished raw materials) you must add 2 magnitudes to begin with (starting at base 1, so final base 3). Furthermore, unless one plans to use vis at the casting of the spell, a Momentary Duration will not suffice, the created arrows would simply blink in and back out of existance before reaching their target(s). One saves themselves such worries by making the Duration Diameter as per the effect previously discussed in the thread mentioned above.
Thirdly, For an added Rego effect I would personally argue that 1. An added magnitude is required precisely because the spell indicates the multiple new arrows are also aimed. If they are Aimed by Rego and not the Archer's inherent bowmanship, they also become magical projectiles (like it or not) and thus subject to MR.
Hmm sorry, Edited to revise my previous conclusion based on rereading of the above thread in which I already suggested a much higher level solution. However you go about it it should definitely be a minimum of level 20 (without added modifiers for larger numbers of arrows, but should (per the thread) have a +2 Group Target modifier. Unless, that is, the intention is to aim all the arrows at one lone individual.