nicholas.robinson,
Welcome to the forum! In the future, please wrap your code in code tags. See forum rules (link in my sig) for how.
As to your query, you need to tell the code what range of cells to monitor. Right now, the code is looking at every single cell in the worksheet to see if it is a "Y" or was deleted. Also, you have the macro calling itself recursively because you enabled events and then performed the ClearContents, which is considered a worksheet change, so code will keep calling itself until it errors because there is no column to the left of column A.
So, basically, if you want to monitor column B from row 2 to row 500:
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