Search and list multiple names

Hi

i have a sheet "data entry" where multiple "item" names are entered, the range of "item" names can be millions, but in the attached sheet i have used only a few as an example.

I need a macro to take all the "item" names from the "data entry" sheet and paste them into the "purchased by month" sheet under the relevant catagories with no duplicate "item" names.

Then in the "avg per item purchased" sheet, i need the average of each of the items over only the months that have data.

The data is currently only running up to column "z", but can go as far as column "xfd"

hope i am explaining this clear enough.

The data entered in red in the sheet is the desired results.

Any help will be greatly appreciated.

Thanks