Code does not contiue after file is opened via dialogue - vba

Question

I'm quite confused right now... I have two modules open_files and start_comparison. From start_comparison I'm calling open_files, which is supposed to open the file open dialogue. The user is then supposed to select one file and hit open. Via start_comparison the user is supposed to open two files. However sometimes (this is where I'm confused) the code opens the first file, but then simply exit's start_comparison occasionally. Sometimes it works, sometimes not, and I have no clue when and why. Below is the code.
What I thought is: When the file dialogue is displayed, one can double click the file and the file will be openend, which would trigger a hidden exit. However, I couldn't confirm this hypthesis. When I step through, everything works fine.
What is your idea about the problem?
Sub start_comparison()
Dim cell As Range
Dim control_file_storage_bins As Range
Dim last_row_CONTROLFILE As Long
Application.ScreenUpdating = False
Set ws_control_file = ActiveWorkbook.ActiveSheet
Range("A2:Z1048576").Clear
Call open_files("PHYSICAL STOCK", 1)
Call open_files("STORAGE BINS", 2)
'Copy stock information
With ws_control_file
.Range("A2:A" & last_row_PHYSICALSTOCK).Value = ws_physical_stock.Range("B2:B" & last_row_PHYSICALSTOCK).Value
.Range("B2:B" & last_row_PHYSICALSTOCK).Value = ws_physical_stock.Range("C2:C" & last_row_PHYSICALSTOCK).Value
.Range("C2:C" & last_row_PHYSICALSTOCK).Value = ws_physical_stock.Range("J2:J" & last_row_PHYSICALSTOCK).Value
.Range("D2:D" & last_row_PHYSICALSTOCK).Value = ws_physical_stock.Range("K2:K" & last_row_PHYSICALSTOCK).Value
.Range("E2:E" & last_row_PHYSICALSTOCK).Value = ws_physical_stock.Range("E2:E" & last_row_PHYSICALSTOCK).Value
End With
Set control_file_storage_bins = ws_control_file.Range("A2:A" & last_row_PHYSICALSTOCK)
For Each cell In rng_STORAGEBIN
If (WorksheetFunction.CountIf(control_file_storage_bins, cell.Value) = 0) Then 'Storage Bin empty
With ws_control_file
last_row_CONTROLFILE = .Cells(Rows.Count, "A").End(xlUp).Row + 1
.Cells(last_row_CONTROLFILE, "A").Value = cell.Value
.Range("B" & last_row_CONTROLFILE & ":E" & last_row_CONTROLFILE).Value = "BIN EMPTY"
End With
End If
Next cell
wb_physical_stock.Close (False)
wb_storage_bins.Close (False)
Application.ScreenUpdating = True
MsgBox "Success!"
End Sub
Other procedure:
Sub open_files(file_type As String, wb_object As Integer)
Dim last_row_STORAGEBIN As Long
MsgBox "Please select the relevant " & file_type & " extract!"
With Application.FileDialog(msoFileDialogOpen)
.AllowMultiSelect = False
.Show
Workbooks.Open (.SelectedItems(1))
Select Case wb_object
Case 1 'Physical Stock
Set wb_physical_stock = ActiveWorkbook
With wb_physical_stock
Set ws_physical_stock = ActiveSheet
last_row_PHYSICALSTOCK = ws_physical_stock.Cells(Rows.Count, "A").End(xlUp).Row
End With
Case 2 'Storage Bins
Set wb_storage_bins = ActiveWorkbook
With wb_storage_bins
Set ws_storage_bins = ActiveSheet
last_row_STORAGEBIN = ws_storage_bins.Cells(Rows.Count, "A").End(xlUp).Row - 1
Set rng_STORAGEBIN = ws_storage_bins.Range("A2:A" & last_row_STORAGEBIN)
End With
End Select
End With
End Sub
In case, here is the private variable declaration:
Private wb_physical_stock As Workbook, wb_storage_bins As Workbook
Private ws_physical_stock As Worksheet, ws_storage_bins As Worksheet, ws_control_file As Worksheet
Private last_row_PHYSICALSTOCK As Long
Private rng_STORAGEBIN As Range
EDIT: I was now checking the procedure open_files with breakpoints. If I set a breakpoint BEFORE Workbooks.Open and run from there again with F5 everything is fine. However, if I set a breakpoint AFTER Workbooks.Open, the breakpoint isn't even triggered. Any ideas?
EDIT2: Previously the macro was started via a short-cut. Now I changed that to an ActiveX-Control and it works fine. Same tested with simple forms and buttons (form control).

Answer 1

If you suspect that opening a file triggers some code, disable events before opening it - this will prevent to execute any (autoexec-) macros withing that file.
Another topic that you should address is that the user might press the "Cancel"-button, else you will run into a runtime error. You can check this with the result of the show-method, it will return False if the dialog was cancelled
With Application.FileDialog(msoFileDialogOpen)
.AllowMultiSelect = False
if .Show then
application.EnableEvents = False
Workbooks.Open (.SelectedItems(1))
application.EnableEvents = True
(...)
else
' You have to make up your mind what to do in that case...
end if
end with