Check if Column Exist

you could use the Match formula to report existing and location of fieldname

Public Function GetFieldPosition(Name As String, FieldNames As Range) As Long
    On Error Resume Next
    GetFieldPosition = Application.WorksheetFunction.Match(Name, FieldNames, 0)
    Exit Function
End Function
Sub x()

    Dim lngFieldCol As Long
    
    lngFieldCol = GetFieldPosition("Customer PO", Range("A1:O1"))
    
    If lngFieldCol = 0 Then
        ' Does not exist
    Else
        ' check position
        
    End If
    
End Sub