facing difficulties when creating table in word c#

Question

Iam  using Interop dll

I able to access 

 

objTable.Cell(3, 6).Range.Text= "Read Point/Test Result"; 

but when i try merge 3.7 or try to write text in Cell(3,7)

 objTable.Cell(3, 7).Range.Text= "Read Point/Test Result"; //error

 

but i have  3 more columns after (3,6 )

 

Error:The requested member of the collection does not exist. c# in system interop

 

Please help on this 

 

 

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