Here index is the column number, if you just pass the column number it will convert it into Excel column( In Alphabets).
But i got, you want it on the basis of value in the excel. Let me do something on that also.
You can use For Each activity and write as Dt.Columns
Declare a variable for For Each Index also
Use If Condition as Item = ADAI and then you can place the invoke code function given by Manoj