You need to make a normal table first, then merge cells to make the structure you want.
Code:
Dim oTbl As Table
Set oTbl = ActiveDocument.Tables.Add(Range:=Selection.Range, NumRows:=3, NumColumns:= _
2, DefaultTableBehavior:=wdWord9TableBehavior, AutoFitBehavior:= _
wdAutoFitFixed)
oTbl.Rows(1).Cells.Merge
oTbl.Rows(3).Cells.Merge