I have multiple columns say 5 of them (1 every two columns starting in column
B and ending in column J). Each column has varying rows of string data. I
want to find the duplicate data across the columns and summarize in another
column 2 away from column J (column L). Hence column L will only show the
duplicate data found in the the 5 other columns. Note that there will not be
duplicate data within any one column. The duplicate data will only exist
across columns.

I am assuming that the best way to do this is to create a VBA 2D array,
define it by the colunn with the most rows of data and then load each column
into the array and search for duplicates from there. I am assuming that I
would then store the duplicates in another array and then dump the results to
column L.

Any insight on how to do this efficiently?

Thanks