Instead of hitting enter twice between entries, you should modify the style
that the bibliography is typed to in have Space After each paragraph. With
the cursor in an entry, click Format | Style. The style in use should
already be selected. Click Modify and in the Format... Dropdown menu at the
bottom of the next dialog, select Paragraph.
See also:
http://www.shaunakelly.com/word/styles/TipsOnStyles.html
Best practice would probably be to create a Bibliography style, which
includes space after and the hanging indent (if you are using that). After
creating a style, you can run a find and replace by style to convert the
existing text.
DM