1. in a cell, input "="
2. select another cell, for example, B15, the edit value is "=B15", which is correct
3. click 'enter'
4. double click another cell to edit
5. in edit mode, use mouse click another cell, for example B20, the edit value will be "B20", which is wrong,
if cell is not formula or start with "=", shall not input cell ref by mouse click