How to Read a Specific Column of Excel and Update Related Values

Can you please let me know how I can use C# to read a specific column values base on the column header?

For example, let say I have a column with header "pAge" how I can loop into the column and update values for the specific rows related to the garbed values. What I want to do is looping in "pAge" column and find all ages over 50 then change the value of those rows in other column "Eligible" to "yes"



The reason that i would like to use the column header instead of column range is because I am getting some data from our clients which are not necessarily in the same order but they have always same name.

Thanks for your time