Use a dropdown to dynamic sort records

What i want to do is to have a dropdown that let's users sort a recordset.
For example: newest first, oldest first, Name A-Z, Name Z-A

So my idea was to set a session variable with the values from the dropdown list on change, having the dropdown in a form and submit that form on change.
Example of the dropdown:

Label: Newest first Value: Date DESC (where Date is the column name to sort)

(This works and sets the correct values in the session variable)

Then add a variable called "Sorter" in the recordset query that reads the session variable and use that variable like this: ORDER BY Sorter
expecting the recordset would be sorted by the value in the session variable.

That's where I got stuck now as the sorting doesnt works.

Did I choose a complete wrong approach or did i miss to pay attention to some detail?