Application.ChangeFileOpenDirectory (Word)

Sets the folder in which Word searches for documents.

The specified folder's contents are listed the next time the Open dialog box (File tab) is displayed. Word searches the specified folder for documents until the user changes the folder in the Open dialog box or the current Word session ends. Use the DefaultFilePath property to change the default folder for documents in every Word session.

ChangeFileOpenDirectory (Path)

Path: The path to the folder in which Word searches for documents.

ChangeFileOpenDirectory "C:\Documents" 
Documents.Open FileName:="Test.doc"