Insert/shapes/choose line or whatever. Then you can format that shape as to
width color etc.
1. You could fill the cell with equals signs.
2. You could have (say) six spaces with underline turned on, then ALT-
Enter, then another 6 spaces, then ALT-Enter again. Adjust the font
size if you want the lines nearer or further apart.
(Just a couple of ways of doing it)
Hope this helps.
Pete