WORKAROUND
Method 1: Use the Line Tool
In Word versions 6.0 and later, use the Line tool on the Drawing toolbar to
draw lines under the text to simulate underlining.
TIP: Hold down the SHIFT key while drawing a line to help keep the line
horizontal.
Method 2: Use an Equation Field to Create an Underscore Character
Create an equation field using the overstrike function to underscore words
or phrases that contain superscript and subscript characters, similar to
the following
Syntax: {eq \o(<Text>,<Underscore characters>)}
as in the following example:
{eq \o(Apple,_____)}
The braces for the equation field are created by pressing CTRL+F9
(COMMAND+F9 on the Macintosh). Type the text between the braces.
In Word for the Macintosh (versions 4.x through 6) create the same
effect with a formula similar to the following
Syntax: {eq .\o(<Text>,<Underscore characters>)}
as in the following example:
{eq .\o(Apple,_____)}
A formula is designated in Word for the Macintosh (versions 4.x through
6) by inserting the special symbol .\ and then entering the one-letter
typesetting command corresponding to the type of element you want to set
up. To create the .\ symbol, press COMMAND+OPTION+\ (backslash).
NOTE: In Word 98 Macintosh Edition, type a plain \ (backslash) instead of
the special .\ (COMMAND+OPTION+\) when creating formulas.
For all versions of Word, in the syntax above, <Text> is the string
containing all the text to be underlined (normal as well as superscript and
subscript text), and <Underscore characters> are the actual characters to
underscore the "Text" characters.
NOTE: The underscore character may not match the one used by the underline
character format command. You may need to experiment with different
underscore characters (different fonts, point sizes, and so forth) to
achieve a continuous underscore effect.