Acrobat JavaScript Convert to LifeCycle JS

Hi Experts,

I would be grateful if you can help on this:

An Acrobat expert from adjacent forum kindly gave me this JS which enables a checkbox field to tick, when text is entered into a text field.  I'm trying to replicate this in ES4.  The JS is:

this.getField("Check Box1").checkThisBox(0, (event.value!=""));

I would be greatful if anyone can explain how I can make this work in ES4.

Kind regards

Kevin