Hi,
You didn't say which version of Word you are using, but from your
description, it seems to me that you are using Word 2007. When you select a
block of text in Word 2007, the status bar shows number of words/total in
document. If you extend the selection, Word will update the number of words
in the selection. If you use your mouse to make a new selection by clicking
on a new location and holding down the left-hand mouse button until you
finish making your selection, Word will also update the number of words in
your selection. However, if you click on a new location and release the mouse
button before making a selection, the number of words in the previous
selection will vanish. Select a new block of text, and Word will show the
number of words/total in document in the status bar for that selection.
By the way, you can see additional statistics about a selection by selecting
a block of text and pressing Ctrl+Shift+G.