VBA to Vlookup cell text and return value as Cell Comment

Hello,

I am a beginner to VBA and I am trying to vlookup the cell values of column A in Datasheet from columns A:B in Mapping sheet. I want to return the value from Mapping sheet column B to Data sheet Column A in the form of a cell comment.

The other caveat is that Column A in data sheet contains duplicate values and I only want to return a comment in the first instance of the cell value. I’ve attached my working file. Your help would be greatly appreciated.

Thank you,
Alex

Edit: Attached corrected file