Drop down list that displays descriptions

I have a spreadsheet that I'm using to organize information that will be entered into a report. Being a government report, the abbreviations they want us to use aren't always intuitive. I've set up drop down lists using the Data Validation tool in my main sheet and the options are linked to cells in the second sheet. However, I'd like the drop down list to display what the abbreviations mean while selecting, but only display the abbreviation in the cell once chosen.

For example, one question is:

"What is the unit of measurement specified by the most stringent regulation?"

The options in my drop down list are as follows:

NH
NM
NP
OT

On my second sheet, where the options are linked from, I have two columns: Code and Description. So, it looks like this:

Code | Description
NH....| pounds per hour
NM....| parts per million
NP....| pounds ber mmBtu
OT....| other

I would like the drop down menu to show both the code and the decription while it's expanded, but only the selected code when entered. I'm not sure if this is possible. I would like to avoid using the VLOOKUP function in an adjacent cell, as is described on a few other help forums, because this portion of the report is 53 questions long (rows) and I have to enter the information for 46 units (columns) and having an extra column for each unit would be long and really unneccessary. One site recommends a combo box, but I don't understand how that works at all.

There may not be a way, but if anyone has any ideas I'd appreciate any help!

Thank you! That worked at first, but I broke it somehow. When I tested it for one list, it worked beautifully.

However, I have 9 different drop down lists in my spreadsheet, so I defined the description sets with names ValuesList_1, ValuesList_2, etc. I used your code to create separate macros for each list and adjusted "=ValuesList" where it occurs in the code accordingly. Some of the abbreviations are three characters, so for those lists with longer codes I changed the 2 in line 11 of the code to a 3. Now none of them work and I'm not sure why

Amazing! Thank you so much, that works perfectly. I definitely could not have figured that out on my own c: