Celestial Aspect Arm Blade Proficiency?

[Bromley20]

I am playing the healer class from Miniatures Handbook in my current campaign and will soon be able to cast Celestial Aspect from BoED. If I choose to gain the arm blade ability, would I be proficient with it? My class isn't proficient with longswords or shortswords and the spell description doesn't state that I gain proficiency with it. Am I correct in assuming that I wouldn't be proficient or is there a rule I am missing somewhere?

[reddir]

I would suggest it be treated as a natural weapon. It replaces an arm and there is no mention of needing any separate proficiency to use well. Same for the Horns.