Product variations within variations

Ive go an issue that I have been trying to work out for a while now,

I build custom computers with lots of different specs and options & the options do change depending on what the customer chooses (I'll try and explain this as best as I can)

Lets say I create a product called “Custom PC Configuration” and add all the variations for say the processors. 3rd Generation processors will have a different set of options available to say 4th Generation processors (Different motherboards available to suit that processor),

so how can I change the variations that are displayed depending on the first choice made?

I hope that makes sense....

Thanks in advance for any suggestions!