As written in the title, I need your precious helps... urgently... :(

The DataGridView does not have any support for merging cells. You can custom paint content across cells, but apart from that you would have to do a lot of work and custom coding to produce merged editable cells.

Go here, and check the code.

Who and "WHY" gave minus for this post??? Hoping he/she will encounter a bigger problem ... Maybe someone will gave a minus for it's post too...

Strange people. Instead of giving you a solution you are looking for, they think the contrary.
Anyway, did that link help you?