I have a template that uses a number of Document Meta data in it's header/footer, like for example the Title, the Subject, Author of the document etc. Is it possible to instruct MS Word to ask user about those fields when they are empt
You can achieve this by using an IF field and a content control linked to the document property of your choosing. This is what the field code should look like, the content in the square brackets is a Title content control which was inserted using Quick Parts -> Document Property -> Title.
Note there must be a space between the content control and the closing speech-mark.
I have uploaded an example document which demonstrate this. The only downside is that after the user enters in a value for the title and clicks away the prompt doesn't disappear, this must be done by pressing F9 to update fields or if you put the whole field in the header footer, by going into print preview.