Visa on arrival Zhuhai

I am a British Citizen and my company supplies technological equipment to Chimelong in Zhuhai. My company wishes me to go there and I would like to do this by obtaining a 3 day VOA at the Macau crossing. However I shall be visiting Singapore and Hong Kong first. I understand that I can only obtain this VOA if I go directly from the UK to Macau from Hong Kong via the ferry at the airport, i.e. without passing through any other country first. Is this correct?