Excel VBA automating - vba

Question

I'm automating excel using VBA. I have created 2 new columns and one of the columns used to have the vlookup function.Сode works properly however I faced one problem. The quantity of Countries_2018.xlsx file can be changed that is why how can I make it dynamic? I mean the data of Countries_2018.xlsx grows and shrinks. Can you check and give me idea? Thank you in advance
Sub Test() Dim Rng1 As Range Dim Rng2 As Range
Dim LastRow As Long
Columns("B:B").Insert
Cells(1, 2) = "Íàïðàâëåíèå"
Columns("S:S").Insert
Cells(1, 19) = "CDR â ìèíóòàõ"
Application.ScreenUpdating = False
Set Rng1 = Range("S2:S" & Range("A2").End(xlDown).Row)
Rng1.FormulaR1C1 = "= RC[-4] / 60"
Range("B2").Select
ActiveCell.FormulaR1C1 = _
"=VLOOKUP(RC[-1],[Countries_2018.xlsx]Sheet!R1C[-1]:R2588C,2,0)"
Range("B2").Select
Selection.AutoFill Destination:=Range(Selection, Selection.Offset(0, -1).End(xlDown).Offset(0, 1))
Application.ScreenUpdating = True
End Sub

Answer 1

Try this:
Sub Test()
Dim Rng1 As Range
Dim Rng2 As Range
Columns("B:B").Insert
Cells(1, 2) = "Íàïðàâëåíèå"
Columns("S:S").Insert
Cells(1, 19) = "CDR â ìèíóòàõ"
Set Rng1 = Range("S2:S" & Range("A2").End(xlDown).Row)
Set Rng2 = Range("B2:B" & Range("A2").End(xlDown).Row)
Rng1.FormulaR1C1 = "= RC[-4] / 60"
Rng2.FormulaR1C1 = "=INDEX([Countries_2018.xlsx]Sheet!C2,MATCH(RC1,[Countries_2018.xlsx]Sheet!C1,0))"
End Sub