MS-Access -- how to create a dynamic query based on listbox value selection

Hello:

I need some assistance with creating dynamic queries.   Allow me to provide some background on the MS-Access (test) database first (see attachment).

Table "Table1":
- It includes two fields: [2-DigitNumber] and [3-DigitNumber].
- For testing purposes, I've added four arbitrary records (2-digit numbers and four 3-digit numbers), respectively.

Query "GenericQuery":
- This query could be deleted afterwards.
- I've merely used the query wizard to generate the SQL code such as: "SELECT Avg(Table1.[2-DigitNumber]) AS Average FROM Table1;"

Form "frmLogin":
- It includes an unbound list box with the following VBA-driven row source (which have not been tied to actions yet):
-- "Run Average of 2-Digit Numbers"
-- "Run Average of 3-Digit Numbers"


My goal (again, testing purposes only right now):
- User opens the database (frmLogin)
- If user selects the list box option "Run Average of 3-Digit Numbers", then a report (or query) opens.  
- The data source is dynamically generated based on the list box's value section of either "Run Average of 2-Digit Numbers" or "Run Average of 3-Digit Numbers".  
- Thus, SQL code for the report's data source is either "SELECT Avg(Table1.[2-DigitNumber]) AS Average FROM Table1;" or "SELECT Avg(Table1.[3-DigitNumber]) AS Average FROM Table1;"

Given that "Run Average of 2-Digit Numbers" is NOT the field name, I somehow have to cross-reference the string to field, e.g., [3-DigitNumber].  
- If that's accomplished, then the new SQL brings up a report that shows "552.5" (the average of the four 3-digit records) vs. "18.5" (the average of the four 2-digit records).

Again, this simple example (using averages) is for creating a general framework first.  Once that works, I will expand the framework in support of the actual database.

Any thoughts as to how this can be accomplished?   Please see attached database as a starting point.

Thanks,
EEH
Testing.zip