Sum columns (duplicates in row header) & delete duplicate cols to leave single unique cols

Hi all,

I currently have a macro that when runs, opens up another workbook on our network drive, selects, copies, pastes and removes some errors into the workbook that contains the macro.

We have some columns that contain duplicate data in one row only, sort of a header row, and the rest of the rows contains dates in the left-most column) and numbers in the rest of the columns.

I've been trying to google and adapt macros I've found, but I can't seem to crack this one (my VBA skills aren't that great). All the macros I've found seem to be row-based and not to do with column duplicates.

I would like to sum the data up for each date in the duplicate columns, remove the duplicate columns so that only a single unique column is left for each header.

Please find a test data workbook that will probably explain the situation better than I have done here. I appreciate the help!

Many thanks,
Kinrossfarm