Complicated Excel Formula Problem

Hello,
I need to create a user form based on several columns of data and what ifs and calculations.
In my user form the user will enter in a pipe diameter

The size of the pipe diameter will offer them various choices of pipe wall thickness

for example, if it is 2" they have ten options, but if it is 3" they 12 different options etc.. (2",3",4",6",8",10",12",14",16") each have their own values.

I want them to enter in manually the diameter. Based on their diameter i want a drop down box to appear in the next column that allows them to choose from the correct array of wall thickness associated with the diameter they enter.

Then, from that selection another option needs to appear in the next column, now they will have to choose the jacket type. The jacket type has several kg/m values, each value corresponding to the wall thickness of the diameter pipe chosen.

So for example.

User enters 2 for two inch pipe
From the drop down box that is shown from a (if a5=2 then use this drop down list) the user chooses 3.58
Now the user chooses from another drop down box whether it is one of five options (for this example Bare)

The next column (based on bare, 2" diameter, 3.58 wall thickness = 5.01) this 5.01 now needs to multiply by a total weight entered by the user in the next column spitting out a total weight.

I can figure out the other cell formulas, but the one i struggle with is how to say if a cell equals one of these 9 numbers spit out one of these 9 drop down lists. is there a way?