The following will work as requested
Code:
Dim oTable As Table
Dim oRng As Range
If Selection.Information(wdWithInTable) = True Then
Set oTable = Selection.Tables(1)
Set oRng = oTable.Range
oRng.Collapse 1
oRng.Select
Selection.SplitTable
Set oRng = oTable.Range
oRng.Collapse 0
oRng.InsertParagraphAfter
Else
MsgBox "Selection is not in a table", vbCritical
End If
Set oTable = Nothing
Set oRng = Nothing