Need Help With Excel Formula Adding Rows

[callred]

I'm creating a calculator that will assist me figuring out student graduation dates. However, I'm struggling to find a formula that will count the number of rows based on the data from the table and the list I've created of terms. I'm not an excel expert in the slightest. 

So I want the result of it counting the terms remaining out from the current term. In this example, 24EW6 is 13 terms out from 22EW1. 

The current term is pulling from a list on the second sheet labeled Terms that has all of the terms listed in order. 

I've figured out to make it count from A2(22EW1) on the Terms sheet, but I can't figure out to make it adjust when you select a different term from the list (Current term is a drop down list from Terms sheet)

[#2]

@callred 

You may find position of final term in term list, position of the current term and subtract one from another. Something like

=MATCH( <ref on cell with final term> , < terms list >, 0 ) -
 MATCH( <ref on cell with current term> , < terms list >, 0 )