Onchange equivalent using Javascript in Adobe Acrobat Pro

So, I've been working on a simple code where, when text is entered/changed/deleted in a target textfield, a box checks to indicate changes have been made to the form in that specific area. Currently I use these two codes: Changes5.checkThisBox(0, event.target.value =! ""); Changes5.checkThisBox(0, document.getField("Lit1").onchange);

Where "Changes5" is the box I want to be checked when changes are made to the textbox "Lit1". Currently, two strange things happen. First, it already checks the box when I click the textbox, not when text is entered/changed/deleted. Second, when the box checks and I click elsewhere (thereby deselecting the textbox where I entered text), the word "true" replaces the current text written in the textbox.

I hope someone sees the error contained in these codes or knows other ways of applying "onchange" or an equivalent code to track changes made by people filling out the form (thereby checking a box).