Insert row here ... or not

I stumbled across this code on another site. It functions like I need it to (i.e. inserts a row after the last row of data along with any equations in the row while also deleting anything that is not an equation) except that in it's current state it defines the last row where the row is to be inserted by locating the last row on the sheet containing data and inserting it there. Instead, I want to be able to restrict the code to a specific range on the sheet where it is to place the new row (i.e. my sheet contains various sections of data ... I want to define the rows that make up one of these sections (let's say A4:A6 named as D_Names) and have the code insert a row at the end of this section instead of at the bottom of the entire sheet). Here's the code:

Private Sub CommandButton1_Click()
  Dim LastRow As Range

  Set LastRow = [A65536].End(xlUp).EntireRow
  With LastRow
    .Offset(1, 0).Insert
    .Copy .Offset(1, 0)
      On Error Resume Next
        .Offset(1, 0).SpecialCells(xlCellTypeConstants, 23).ClearContents
      On Error GoTo 0
  End With
End Sub