Excel VBA : how to merge cells in winword table with for... next

[justuptou]

Under Excel VBA operating, I have to merge the cells in winword table with For ... Next function.
but system error code was shown '5941' when run "Rng.Cells.Merge", I cannot fixed the problem,
Could anyone guide me to modify that, thank you very much.

Error Message :

Run-time error '5941':
The requested member of the collection does not exist.

Target : Cells(1,1 & 2,1).Merge, Cells(1,2 & 2,2).Merge, Cells(1,3 & 2,3).Merge &
Cells(1,5 & 2,5).Merge, Cells(1,6 & 2,6).Merge

Figure : Winword Table below

1,1	1,2	1,3	1,4	1,5	1,6
2,1	2,2	2,3	2,4	2,5	2,6

Coding :

Sub mergeCellinTable()
        Dim ObjWord
        Set ObjWord = CreateObject("Word.Application")
        
        Dim objDoc
        Set objDoc = ObjWord.Documents.Add
        
        ObjWord.Visible = True
        objDoc.Activate

        With ObjWord
             Dim Table1
             
             Set Table1 = objDoc.tables.Add(Range:=objDoc.ActiveWindow.Selection.Range, _
                                                   NumRows:=6, _
                                                   NumColumns:=6, _
                                                   DefaultTableBehavior:=wdWord8TableBehavior)

             Dim Rng
             For I = 1 To 6
                 If I <> 4 Then
                    With objDoc.tables(1)
                         Set Rng = .Cell(1, I).Range
                             Rng.End = .Cell(2, I).Range.End
                             Rng.Cells.Merge
                             Rng.Text = "Merged Column Cells"
                    End With
                 End If
             Next I
        End With
End Sub