plugin=diff is not implemented.
http://yellow.ribbon.to/~tuotehhou/index.php?%2BWinForm%2BDataGridView%E5%86%85ComboBox%E3%82%BB%E3%83%AB%E3%81%AESelectedIndexChanged%E3%82%A4%E3%83%99%E3%83%B3%E3%83%88%E3%81%AE%E6%A4%9C%E5%87%BA
plugin=diff is not implemented.