Output set elements - again

Last week there were several Forum posts regarding Output Sets. 
We have another question regarding output set elements.

A request was received to create an output set element that includes a drop-down list.
We completed this request, but our user would like to select multiple values from the drop-down list.

For example, the new element allows a user to select "Season 1" from the drop-down list - but only one value from the drop-down list.
In this one output set element, our user would like to select "Season 1" and "Season 2" from the drop-down list. 

Is this possible? 

If not, I advised our user we may be required to create an output set element for "Season 1", and a second for "Season 2", etc.


Thanks
Wendell Baskin
Bass Hall - Fort Worth