Prevent Changing Data In Column But Allow Row Insertions / Deletions

I am trying to create a worksheet_change event that will prevent a user from changing or deleting data in the totals column of my worksheet yet allow them to insert rows and delete rows on the worksheet. I have a few issues I can't get resolved. First, if I delete a row and then click the undo message, I get my error message about trying to change the totals. Second, I cannot copy and insert copied rows. I can only insert blank rows. Here's my code and data.

Private Sub Worksheet_Change(ByVal Target As Range)
Static lngRow As Long
Dim iStrtRow As Integer, iEndRow As Integer, rRowMrkr As Range

[Code]....

Defined range names: "Header" in cell A1 and "Totals" in cell A12