All fields have a name. You can find out what the name of a field is by right clicking on a field, choosing properties, and looking in the General tab.
For example, if a text field's name is "Text1", the script would be:
getField('Text1').display = display.hidden;
Thank you for your answer. However, I may have miscommunicated. I'm trying to select a textbox, not a textfield. For example, in Acrobat Pro I go to Tools > Content Editing > Add Text. The text I'm adding with the Add Text tool is the text I'm trying to select. Maybe I'm going about adding the text the wrong way to be able to select it. Again, thanks for the help.
Text boxes are a type of annotation. You should look at the properties of the Annotation object.
There is a "seqNum" property which is a sequence number for the annotation on the page, but I have not tested it.
Having re-read your original post, however, I don't think you should use text boxes. The text "What day will you stop working?" should appear in a normal text field, as should the text field for the user to enter a date.