What Word does when you type '---'<Enter> is to apply a bottom border to the paragraph above. The border width will be the same as the paragraph width, so narrowing the paragraph will narrow the border.

If you want a line that is less than the paragraph width, the simplest method is probably to insert an autoshape line if the required width.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]