Resume to a label not working as expected - vba

Question

I am having an issue using Resume and although I have found another solution by using an On Error GoTo, I am still confused as to why the code below doesn't work. The initial error occurs because the sheet name "Sheet_1" is already taken. This means that, in the watch window, err.number has a value of 1004 just before the Resume NameAgain is executed. Rather than clear the error and jump back up to the label, an error 20 occurs(resume without error), and the code moves to the End If line.
Given that there is an active error 1004, I can't understand why it acts as though there isn't an error. I have searched the site for Error 20 issues but nothing really resolved this for me or made me understand the logic behind it. Any help is much appreciated.
Sub ErrorTest()
Dim i as integer:i=1
NameAgain: On Error Resume Next
Worksheets("Main").Name = "Sheet_" & i
If Err.Number = 1004 Then
i = i + 1
Resume NameAgain
End If
End Sub
Update after paxdiablo comment:
The above was a poor attempt at trying to replicate but simplify a problem I was having. The section of code I am working with is below:
Activate CheckBook to use ActiveWindow
CheckBook.Activate
Set DestSheet = CheckBook.Worksheets.Add(After:=CheckBook.Sheets(1))
On Error Resume Next
v = 1
NameAgain: DestSheet.Name = ExpBookName & "_" & v
If Err.Number = 1004 Then
v = v + 1
Resume NameAgain
End If
On Error GoTo 0
ActiveWindow.DisplayGridlines = False
Set DestCell = DestSheet.Range("A2")
So the solution is to move the On Error Resume Next to the label line and use GoTo in place of Resume.

Answer 1

The resume statement is a means to, from within an error handler, go back to some point in your main (non-error-handling) code and resume execution.
In this case, you've explicitly stated you want to automatically resume next in the event of an error.
This is functionally equivalent to (VB-like pseudo-code):
line:
on error goto handler
cause error
resume line ' not in an error handler at this point '
handler:
resume next
So you're not technically in an error handler at the point where you try to resume to the label.
The right statement for what you're trying to do would be a simple goto rather than resume.

Answer 2

A more correct solution is to write code that does not deliberately generate errors or which does not use Goto.
Public Function GetNextSheetName(ByVal ipWb As Excel.Workbook, ByVal ipStemName As String) As String
Dim mySheet As Variant
Dim mySD As Scripting.Dictionary
Set mySD = New Scripting.Dictionary
For Each mySheet In ipWb.Sheets
' mySd.Count is a dummy entry to satisfy
' the Key and Item requirements for .Add.
' we are only interested in the Keys
' for use with the .Exists method later
mySD.Add mySheet.Name, mySD.Count
Next
Do
DoEvents
Dim myIndex As Long
myIndex = myIndex + 1
Dim myNextSheetName As String
myNextSheetName = ipStemName + "_" & CStr(myIndex)
Loop While mySD.Exists(myNextSheetName)
GetNextSheetName = myNextSheetName
End Function
Which now allows
Set DestSheet = checkbook.Worksheets.Add(After:=checkbook.Sheets(1))
DestSheet.Name = GetNextSheetName(checkbook, ExpBookName)
ActiveWindow.DisplayGridlines = False
Set DestCell = DestSheet.Range("A2")