If you start Word, click on Help, and search for "drop-down box",
then you would find the following two help topics at your fingertips:
"Fields for use with forms"
"Add, remove, or change the order of items in a drop-down list"
You can find more information about creating userforms at
> I need to insert a drop down box into a Word document that lists several
> choices that are selected when you click them. How do I do this?