Maybe I did not understand the original question ?
First I was assuming that there is a list used to fill Combo1, and that it would look something like this:
Then, I was assuming there is a "bigger list", from which you only choose the items for Combo2 where the first column agrees with the selection in Combo1, something like this:
List that fills Combo1
If my assumptions are incorrect, the suggested code would need to be revised. But, this is how it works ...
List Used to decide what goes in Combo2
First, it grabs the range that was used to fill Combo1
Then, reads which item was selected
Next, you need to tell it where to find the "bigger list", so it can decide what needs to populate Combo2:
After that, it reads down the list and if it finds an entry that is what what chosen in Combo1, it takes the value in the adjacent column and adds it to Combo2's list.
If you have more than 2, the code will need to be more sophisticated, I'm afraid. Any way you can post a skeleton of your workbook?