I'd like to begin by thanking any one who helps me solve this problem, your time is greatly appreciated.

First post on here, let's do this!

Provided on this post is my Excel Sheet. The objective of this sheet is to calculate pressure when a pipe material and grade are selected. I have the data validation in the first cell ask for "Carbon Steel" or "Stainless Steel". The next cell asks for spec/grade. When Carbon Steel is input, I have the next cell ask for certain specs, but when I select the drop-down list, there is a space between the specs. When I choose "Stainless Steel", there are no spaces and the list produces exactly as I need it to. This is rather hard to explain so following along with the sheet may help.

Also, I'd like for the tables to not return errors when I change from "Carbon Steel" to "Stainless Steel" when the specs don't match up. For example: If I choose a Carbon Steel and a Grade, then switch the first cell to "Stainless Steel", the table fills with errors because the Stainless Steel spec doesn't match, until I select the Stainless Steel Spec from the second validation. I know this sounds entirely complicated, but when you view the excel you'll see that it's not too complex.
Pipe Calculations.xlsx