How can I add and track inventory based on the number of units only and not the dollar value?

Hello,

I own and operate a jewelry manufacturing business where I need to keep track of the precious metals I use when manufacturing jewelry. I am using QuickBooks Online Plus.

When I create an invoice, I want to write how much gold I ended up using, and I want that "x" amount to be reflected in my total inventory. I do not want the $ amount, because gold prices change daily.

For example, let's say I own 3,000 grams of 24K Gold.

Client A used my services to manufacture a ring, and that ring needed 5 grams of 24K Gold.

I want the invoice to show the labor cost as a dollar value, and the 24K Gold amount as a unit/gram and NOT a $ value.

That way, when I look at my total inventory, it will show 2995g 24K Gold, and it will not be affected by fluctuations in the market.

Is there anyway I can do that? Or am I stuck using the dollar value and having to update it every day, and sometimes every couple hours?

I really appreciate the help.