Good to see you back, @Firstcarpentry.

Computing three different units are unavailable in QuickBooks Desktop (QBDT). Although, you can compute it manually then apply it in your transactions or find a third-party app that has this feature. I'll share my perspective on entering your computation in QBDT below.

You can enter the Quantity as 100 then, add the 8 board foot (bdft) multiply to the price that is $1.50 under the Description column. Lastly, enter the total amount for the 8bdft x $1.50 under the Amount column. That will give you the total amount of $1200.00.

I added a screenshot for your additional reference.

Also, if you want to venture to our third-party apps, you can check out this link: https://desktop.apps.com/home.

I'll be right here to continue helping if you have any other concerns. Have a good one.