underline.

doc did not give me a last name so I would like to put an underline in the area the last name should be, but I cannot get an underline there with no text.

In Word 97 I used to hold F8 and the space bar down until I wanted the line to stop, but in Word 2007 that does not seem to work. I tried highlighting the area with the mouse and then hitting the underline icon with the mouse and also using Control U, but neither are working. Any suggestions.