Clear text box

When selecting a checkbox I want to export the data to a text box. I have this code.

Trigger: Mouse Up

Action: Run a JavaScript

var one = this.getField("Check Box2");

var two = this.getField("Text6");

{two.value=one.value}

When clicked it puts the export data from Check Box2 into Text6. However, if I want to change my selection, it will not allow the new export data to be exported into Text6 as it already has the data from the previous selection in it. Any help on the code to clear Text6 before a selection is made in Check Box2 would be much appreciated.