Lime is used to raise the pH of the soil, Rosemary. So you should do a soil test before you apply it, because that's really the only way to determine if you need it. You can get one through the University of Maryland's extension service:
Thanks for the reply. I do not have a way to get to University of Maryland. I will just continue to treat my lawn like I have been doing.
@Rosemary they probably have an option for you to mail in the samples, if you can't make it to one of their offices, though usually each county will have a county extension office that is associated with the university.