Quoting from Word help:
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FIELDS FOR USE WITH FORMS
{ FORMCHECKBOX }
{ FORMDROPDOWN }
{ FORMTEXT }
These fields insert a check box, a drop-down list, or a text box
in a form. You cannot insert or modify these fields directly.
They're inserted by the Check Box Form Field, Text Form Field,
and Drop-Down Form Field buttons on the Forms toolbar. To edit
these fields, you must use the Form Field Options button on the
Forms toolbar.
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ADD, REMOVE, OR CHANGE THE ORDER OF ITEMS IN A DROP-DOWN LIST
1. Open the template that contains the form you want to change.
2. Remove protection from the form template by clicking
Protect Form on the Forms toolbar.
3. Double-click the drop-down form field you want to change.
4. Do any of the following, and then click OK:
• To add an item, type the name of the item in Drop-down
item box.
• To delete an item, click the item in the Items in
drop-down list box, and then click Remove.
• To move an item, click the item in the Items in
drop-down list box, and then click the Move arrow buttons.
5. If you want to clear any information that you might have
entered while working on the form, click Reset Form Fields on
the Forms toolbar.
6. Protect the form by clicking Protect Form on the Forms
toolbar.
Note: The first item in the Items in drop-down list box is the
one that appears by default in the drop-down list. To move the
most frequently selected item to the first position, use the Move
arrow buttons.
