Sub TableRowAtLeast()
  Dim iSize As Long, aCell As Cell, aTbl As Table
  For Each aTbl In ActiveDocument.Tables
    For Each aCell In aTbl.Range.Cells
      If aCell.HeightRule = wdRowHeightExactly Then
        iSize = aCell.Height
        aCell.HeightRule = wdRowHeightAtLeast
        aCell.Height = iSize
      End If
    Next aCell
  Next aTbl
End Sub