I dont completely understand what you are asking, but here is what i think you are asking for from what i read. You want to go through the entire column 'N', and if the value in N is 18, then you want a new row inserted below it? if this is correct then the below code will achieve this.
Dim URange, LRange
Dim BCell As Range
Set URange = Range("N1")
Set LRange = Range("N" & Rows.Count).End(xlUp)
For Each BCell In Range(URange, LRange)
If Val(BCell.Value) = 18 Then