filling cell in column "a" if data present in column "b" issue.

hello,
i am working on a spreadsheet for work and one of the tasks I'm trying to accomplish is when i fillout a cell in the "Part #" column(B) to auto fill the equivalent cell in the "CUST #" Column(m) with the number 808849. i have this working except it over rights my header row(row 7) because the label "PART #" means that cell is filled so it overrights "CUST #". i have tried to limit the range to row 8+ but it then freaks out and dumps 808849 into a bunch of random fields. in the attached file i had to sanitize it due to confidentiality. if it would help i can fill it back up with fake info. i know everyone says this but i am pretty new to VBA scripting so i'm sure I'm missing something very obvious, also i know this script is a bit useless by itself but it's only step one to a much larger intent.

Option Explicit

Private Sub Worksheet_Change(ByVal Target As Range)
Dim RNG As Range
'Dim ws As Worksheet
'Set ws = Worksheets("Sheet1")
'Dim lastRow As Long

    Application.EnableEvents = False
    On Error Resume Next
    'lastRow = ws.Cells(ws.Rows.Count, "B").End(xlUp).Row
    'MsgBox (lastRow)
    Set RNG = Range("B:B").SpecialCells(xlConstants)
    
    If Not RNG Is Nothing Then
        RNG.Offset(, 11) = "808849"
    Else
        Cells.ClearContents
    End If
        
        Application.EnableEvents = True
    
End Sub

Blank_template.xlsm

Hi Tim

I cannot see where you are controlling your macro.

This is your basic problem. Insert the following line.

'if row <=8 or comumn <> b then exit
if target.row<9 or target.column <> 2 then exit sub

Option Explicit

Private Sub Worksheet_Change(ByVal Target As Range)
Dim RNG As Range
'Dim ws As Worksheet
'Set ws = Worksheets("Sheet1")
'Dim lastRow As Long

if target.row<9 or target.column <> 2 then exit sub

    Application.EnableEvents = False
    On Error Resume Next
    'lastRow = ws.Cells(ws.Rows.Count, "B").End(xlUp).Row
    'MsgBox (lastRow)
    Set RNG = Range("B:B").SpecialCells(xlConstants)
    
    If Not RNG Is Nothing Then
        RNG.Offset(, 11) = "808849"
    Else
        Cells.ClearContents
    End If
        
        Application.EnableEvents = True
    
End Sub

Could this be of help?

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim Rng As Range
    On Error Resume Next
    Set Rng = Range("B:B").SpecialCells(xlConstants)
    If Not Intersect(Target, Rng) Is Nothing Then
        Application.EnableEvents = False
        Target.Offset(0, 11) = "808849"
        Application.EnableEvents = True
    End If
End Sub

thanks for the help this solved my problem completely