Merge more than two cells in msword Table document using C#

I wants to merge more than two cells in word table by using C# micrososft interop. i am able to merge two cells using following code. 

objTab1.Rows[1].Cells[1].Merge(objTab1.Rows[2].Cells[1]);

 

but, my requirement is to merge more than two cells. please can anyone help me out of this.

 

Thanks in advance.