Excel vba - select first column - excel

Question

i'm trying to make some changes in excel file using VBA, the file contains many sheets
the code should make changes for 1st sheet then go to the next and next,
but after makes the changes in 1st sheet and go to 2nd it shows:
Error no 1004 "Object error".
Here the code:
Sub AddRefNo()
'This code adds Reference Number to All BOQ sheets based on Worksheet Name
'select the first sheet
Worksheets(4).Select
' Work in One Sheet
Do While ActiveSheet.Index < Worksheets.Count
'add new Column
'the error happens here
Columns("A:A").Select
Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
Range("A1").Select
ActiveCell.FormulaR1C1 = "Ref. No"
Range("A2").Select
'Find Sheet Name
MySheet = ActiveSheet.Name
'creat numbering system
Dim Noe As String
Noe = 0
' Find the last row
Dim LastRow As Integer
LastRow = Range("E" & Rows.Count).End(xlUp).Row
Range("E2").Select
'repeat steps to the last row
Do While ActiveCell.Row < LastRow
'checking if the cell is not blank
Do While ActiveCell.Value <> ""
ActiveCell.Offset(0, -4).Select
Noe = Noe + 1
ActiveCell.Value = MySheet & " - " & Noe
ActiveCell.Offset(0, 4).Select
ActiveCell.Offset(1, 0).Select
Loop
ActiveCell.Offset(1, 0).Select
Loop
Noe = 0
Range("A1").Select
ActiveSheet.Next.Select
Loop
Worksheets(1).Select
End Sub

Answer 1

Here is a way to reliable loop through your worksheet index numbers:
Sub AddRefNo()
Dim wb As Workbook: Set wb = ThisWorkbook
Dim ws As Worksheet
Dim x As Long
For x = 4 To wb.Worksheets.Count - 1
Set ws = wb.Worksheets(x)
'Your code to work with ws as a parent
Next x
End Sub

Answer 2

This should do the trick if you want to loop from sheet 4:
Option Explicit
Sub AddRefNo()
'Declare a worksheet variable
Dim ws As Worksheet
'Loop every sheet in the workbook
For Each ws In ThisWorkbook.Worksheets
If ws.Index < 4 Or ws.Index = ThisWorkbook.Worksheets.Count Then GoTo nextWorksheet
'Reference always the sheet
With ws
'Calculate last row
Dim LastRow As Long
LastRow = .Cells(.Rows.Count, "E").End(xlUp).Row
'Insert a column
.Range("A:A").Insert
.Range("A1") = "Ref. No"
'Put the name sheet + reference starting from 1
With .Range("A2:A" & LastRow)
.FormulaR1C1 = "=" & Chr(34) & ws.Name & Chr(34) & "&ROW(RC)-1"
.Value = .Value
End With
End With
nextWorksheet:
Next ws
End Sub