Imports Microsoft.Office.Interop.Excel

Public Class Form1
    Dim ExApp As New Application           'Приложение Excel  
    Dim ExWB As Workbook                   'Книга Excel  
    Dim ExWS As Worksheet                  'Лист книги Excel  
    Dim ExWB_Dic As Workbook                   'Книга Excel  
    Dim ExWS_Dic As Worksheet                  'Лист книги Excel
    Dim xlLastCell, xlDestRange As Range
ExWS = ExWB.ActiveSheet
 For i As Integer = 1 To ExWB.Sheets.Count ' переход по листам книги
    
            ExWS = ExWB.Sheets(i)

            Rayon_ = ExWS.Cells(1, 1).value

            xlDestRange = ExWS.Range("A1:E20").EntireColumn
            xlDestRange.Insert(xlShiftToRight)

            Dim LastRow_, LastColl_ As Integer
            xlLastCell = ExWS.Cells.SpecialCells(xlCellTypeLastCell)
            ' Получаем значение последней строки
            LastRow_ = xlLastCell.Row
            LastColl_ = xlLastCell.Column
     Next
 ExApp.Quit()
End Sub