Word – Microsoft Word Variable without Macro

In Word 2007 you can use a Quick Part to create reusable content. From the help docs:

Create a reusable content building block

1. Select the text or graphic that you want to store as a reusable building block.
2. On the Insert tab, in the Text group, click Quick Parts, and then click Save Selection to Quick Part Gallery. Or press ALT+F3.
3. Fill out the information in the Create New Building Block dialog box:
   • Name: Type a unique name for the building block.
   • Gallery: Select the gallery that you want the building block to show up in.
   • Category: Select a category, such as General or Built-In, or create a new category.
   • Description: Type a description of the building block.
   • Save in: Select the name of the template from the drop-down list.
   • Options: Select Insert content in its own page to ensure the building block is placed on a separate page. Select Insert in own paragraph for content that should not become part of another paragraph, even if the user's cursor is in the middle of a paragraph. Select Insert content only for all other content.

You can find more detailed help as well in Word 2007 by clicking the Insert Tab > Expanding Quick Parts > F1 for help on Quick Parts.

Edit 1
Apparently Quick Parts are not dynamic which means child parts will not be updated when the parent is updated. Some possible alternatives:

1. MSDN: Exploring the Dynamic World of Word 2007
2. Word Custom Properties: How to Improve Productivity

Edit 2 (requested by OP to be added to answer)

I think that for my use the Comments document property works best. I need one value in many places and I need it to update automatically. The advanced doc properties don't update automaticaly (despite all efforts to the contrary). But the basic document properties do.

On the Review tab, there's an option to compare documents and merge them into one: