javascript in text field on PDF

Hi

Can anyone help with a javascript for this scenario:

I have a full length line of static text which is set in indesign, at the beginning of the line sits a dynamic text form field, within this field we have the following javascript that makes the text within the box dissappear when end user fills in the field.

var message = 'final/balloon payment'

if (event.value == '') {

    event.target.display = display.noPrint

    event.value = message

} else {

    event.target.display = display.visible

}

PROBLEM (see link) -  The text field when complete leaves empty character space until the static text begins. Is there any way the complete line can be dynamic? So it looks a complete line with no white spaces???

http://ftp.splashprinting.co.uk:82/f/Screen%20Shot%202018-01-04%20at%2015.40.47.png

thanks in advance, note I am not a coder, i found the existing script online.