Steven,
We had a similar requirement for one of our forms. What we did was to create a multi line text field called additional_guidance.
Then in the mouseEnter event of each field we had the following Formcalc:
additional_guidance = "This is further information about this checkbox"
On the mouseExit event we had:
additional_guidance = null
Alternatively, you could set up the root container as a flowed content. Then the checkboxes would be in a positioned content subform and subsequent fields in another positioned subform. In between these you would have a hidden invisible flowed subform which contains the notes in a text field or static text. This would appear or be hidden depending on mouseEnter events or click events on buttons.
If you need to provide alot of detailed information in a formatted layout, then you could set up a page for each checkbox (or one page for all of the checkboxes) at the end of your form (e.g. called checkbox1_notes). You would set the presence to hidden. Then your button next to checkBox1 would have javascript like this in the click event:
checkbox1_notes.presence = "visible";
xfa.host.currentPage = xfa.host.numPages - 1;
Remember to put a hide button on this help page with the folloeing javascript in the click event:
checkbox1_notes. presence = "hidden";
xfa.host.setFocus(xfa.form.form1.p1.checkbox1); //this would be the full reference for your object
Good luck,
Niall