Dropdown selection exported value displayed in other field on mouse rollover

Before selecting a Dropdown item, I'd like to have a text box ("Text1") display the exported value as I rollover each item in the Dropdown with the mouse. I am able to successfully do this by entering the following Custom Keystroke Script on the Dropdown's Format tab:

if (!event.willCommit){this.getField("Text1").value=event.changeEx;}

However, this only works when using the keyboard's up/down arrow keys to step through the Dropdown list items. So rather than using the arrow keys, is it possible to display the exported values by rolling over each item with the mouse pointer before committing to a final selection?