Concatenate columns in Excel

Hey actually i have a prob,



i have 4 columns in my excel sheet, among them based on 2nd column i have to concatenate the contents of 4th column irrespective of 3rd column.


sno: Department Salary Emp
1 Accounts 15000 Kiran.K
2 Accounts 12000 Rosy Marry
3 Accounts 18000 Vandana
4 Statistics 20000 Karthikeya
5 Statistics 20000 Ramana
6 Statistics 18000 Naresh



Among these entries i need result as follows..


Sno Department Emp
1 Accounts Kiran.K, Rosy Marry, Vandana
2 Statistics Karthikeya, Ramana, Naresh


Can anybody help me please as this format killing most of my time..