Underling Exsisting Fonts

[ugom...@hotmail.com]

Ok, I am new here and I can't believe I found this bulleting...here's
what I need.

I am running Fontographer 4.1 for Mac and I need to Underline an
existing font like AGaramond.
I have tried to do this manually by copying the underscore character
and pasting it to the rest of the chararcters, then I manually adjust
the widths to the correct width of the character Block.

After I do this and generate a Type1 font and install it into my system
the Underlines look crooked and uneven.

Is there a better way to create an underline for existing fonts? Do I
need a plug for Fontographer?

Any input would be appreciated!

Thanks,

Hugo