Macro to generate directory subfolders based on new entries only in tracking sheet

[kelle]

I'm working on a tracking sheet for a manager that includes automatically-generated file numbers for any new content--so whenever I enter a new line, the number "2018-x" (where "x" is the next number in the series) populates. Because these tracking items will include follow up content, I need to write a macro that will automatically populate the directory folder where the Excel document is with all of those numbered folders--2018-1 through, say, 2018-32--so that I can save content to them. HOWEVER, I want to make sure that at no point does the macro over-write previous folders. How would I go about doing this? I'm assuming running it on a save event, but... I have no idea! Help please Thanks in advance!