Question
I HAVE A SMALL LAWN LEFT. 3YEARS AGO I HAD AN EXTENSION BUILT AND THE DRAIN UNDER THE LAWN WAS BLOCKED OFF AND IN CONSEQUENCE THE LAWN IS NOW VERY DAMP I HAVE AERATED IT AND LAWN RAKED COULD YOU ADVISE ME IF SOME KIND OF SAND WOULD BE APPROPRIATE AND IF SO WHAT KIND
                        THANKING YOU IN ANTICIPATION

Answer
Good afternoon K. Mason:
If you cannot find a way to get around the blocked area what you will probably have to do is to install a new drainage tile system. To do this you will most likely need some help. Check with your local soil and water conservation district office for advice. Essentially, what it means is that you will have to lay a grid with trenches similar to foundations around the house. Then connect to a central channel that drains into a ditch or something like that. Adding sand will not help.

The following web sites could be of help to you.

How to install a drainage system in your lawn: This is information from Great Briton but is just as good here in the U.S.A.
Copy and paste to your browser and hit "GO"
http://landscaping.about.com/gi/dynamic/offsite.htm?site=http://www.landsteward....

Scotts Lawn Forum Question on Lawn Drainage similar to your problem:
Copy and paste to your browser and hit "GO"
http://forums.lawncare.com/forum/messageview.cfm?catid=6&threadid=5140&enterthre...
I am sorry I cannot give you an easier answer.
Have a good lawn!
Floyd McMahon