You seem to have 2 choices.
1- simply click the menu button on the top left of word and select Close
2- Modify the Quick Access Toolbar to include the Close button.
You will need to select Word Options from the bottom of the Word Menu Button list
Select Customize in the left panel
Open the drop down and select “All Commands” in the “Choose Commands From” list.
Scroll down to find Close then click the arrow to ADD it to the “Customize Quick Access Toolbar” pane.
Select OK and this should be available to you in the future each time you open a Word document.
It is probably possible to do what you want programatically but that is more than I am wiling to tackle.
I hope this helps you out.