Sell an item online with different variations having different prices

[CountryClay]

Hi!  I have a ceramic shop and will be holding workshops. The particular workshop I'm working on now is Christmas trees.  I want customers to pay for the class online according to the way they want to finish their tree.

I have room for 8 students who will all begin with a basic unfinished tree.  There are 4 variations of finishes they can choose from and each has a different price.  My basic tree inventory needs to be 8 and the finish options purchased need to add up to no more than 8.  Example:  I have 8 basic trees available for workshop customers.  Customer #1 wants to finish it with glaze.   Now I have 7 basic trees available.  Customer #2 wants to finish it with acrylics.  Now I have 6 basic trees left.  Customer #3 wants to use glaze.  That leaves 5 basic trees for others to choose from.

How do I set up the "Christmas Tree Workshop" item to begin with an inventory of 8 and reduce inventory by number of paid finish selections as well as come up with the correct price?  I don't want to assign an inventory number to each variation.  What if all 8 customers choose glaze?  Then it would look like I have 24 trees left.

I hope this makes sense.  Thanks for any help!

[CountryClay]

I actually figured it out.  I need to use Modifiers instead of variations.  Works like a charm!