Double click event

Hi, got a VBA question.

I've got this sheet with data in cell a1. I'd like the data to move 1 cell to the right when you click on the cell. I've set it up with the double click event and it works when you double click on the sheet. How do I get it so it only moves when I double click on the actual cell, rather than the sheet?
Please find the attached example.

Many Thanks
Harry