Intersect not working if target range gets bigger - vba

Question

I am relatively new to VBA and I need help with this please.
I have a private sub within a sheet and I want it to autofill formulas adjacent to a dynamic named range, if the size of the range changes.
(edit) I am pasting data from another worksheet into this one columns A-M. My dynamic range is defined as =OFFSET($A$1,1,0,COUNTA($A:$A)-1,13). The first If statement should exit the sub if there is no data in column M and I had the destination calculating the last row of column M because I want to fill the formulas in N:O so that they cover the same number of rows as column M.
This is my code and it works if the size of the range gets smaller (i.e. if I delete rows from the bottom), but not if it gets bigger and I can't work out why!
Private Sub Worksheet_Change(ByVal Target As Range)
If Me.Range("M2").Value = "" Then
MsgBox "No Data!"
Exit Sub
Else
If Intersect(Target, Me.Range("rngOracleInvoices")) Is Nothing Then
Application.EnableEvents = False
Dim Lrows As Long
Lrows = Me.Cells(Me.Rows.Count, "N").End(xlUp).Row
Me.Range(Me.Cells(3, 14), Me.Cells(Lrows, "O")).ClearContents
Me.Range("N2:O2").AutoFill Destination:=Me.Range("N2:O" & Me.Range("M" & Me.Rows.Count).End(xlUp).Row)
End If
End If
Application.EnableEvents = True
End Sub
I put the last bit into a separate macro to test if it works on its own and for some reason, when I run it, the autofill goes all the way up to row 1 and overwrites the formulas, which is weird because I use that code a lot and it's never done that before. What have I done??!!
Also, if there is a better way to do the autofill I'd appreciate if someone could let me know what it is because I just cobbled that together from bits I found on forums :)
Thanks,
Soph

Answer 1

In this line Me.Range("N2:O2").AutoFill Destination:=Me.Range("N2:O" & Me.Range("M" & Me.Rows.Count).End(xlUp).Row) you calculate your last row on the column M so if it is empty it'll give you 1 and autofill your formula on row 1.
So start by calculating it on the good column (my guess is O)
You can also simply define an Integer variable to test it and if it is inferior to 2, change it back to 2, 3, 4 or whatever you want.
For your dynamic range, we might need some precision.
And for the AutoFill, you could just select manually the range N2:02 and then double-click on the bottom right square (the one you drag to autofill) and it'll autofill as long as there data in adjacent cells! (give it a try ;) )