display unique list in dropdown in each subsequent cell

Hi,

I am looking to get a list of unique data without any duplicates to be displayed in dropdown in G column and in gets update with new data in subsequent cells as well in previous cells.But the data so displayed in G column should be unique to F column.For eg.

if I type in F12 = Ram Kapoor,then it will search all the Ram Kapoor corresponding list of data in G column and display in dropdown without any duplicates in G12.
But if in F12,if the data is new type and does not exist then it will allow one to do entry in G column that will be updated in next cells and previous G column cells.

Hope I could be able to make it understand.

Code is included from http://www.excelforum.com/showthread.php?t=1148579

Hope modification in it will ease.