Control Sizing of Dropdown on HTML Screen Using HTML Composer

[John Lewis]

I am building an HTML page using HTML Composer in App Studio.  One of the elements I am creating is a multi-select dropdown.  When I run the page and click on the dropdown, I get a little window with checkboxes next to all the values in the dropdown, enabling me to check any values I want to see in the report.  This little window only shows 6 values by default, although there is a scroll bar and I can resize this window as needed.  My question is  -  is there a way for me to control the size of the little window?  I'd like it to be longer to show more values when clicking on the dropdown.

I have attached a screenshot of the HTML page with the dropdown window I am talking about.

I am on WebFOCUS v9.2.3.

Thanks!