error handling in VBA - excel

Question

i have a sub that looks like this:
Sub open_esy(filename, p As String, p1 As Integer)
Dim fileLocation As String
Dim iFileNum As Integer, findblank
Dim letter_temp0 As String, letter0 As String, letter1 As String
Dim i As Integer
Dim j As Integer
i = 16
If Dir("\\Tecan3\output\" & filename & "*esy") <> "" Then
fileLocation = "\\Tecan3\output\" & Dir("\\Tecan3\output\" & filename & "*esy")
ElseIf Dir("\\Tecan_2\output on tecan 2\" & filename & "*esy") <> "" Then
fileLocation = "\\Tecan_2\output on tecan 2\" & Dir("\\Tecan_2\output on tecan 2\" & filename & "*esy")
ElseIf Dir("\\Tecan1\tecan #1 output\" & filename & "*esy") <> "" Then
fileLocation = "\\Tecan1\tecan #1 output\" & Dir("\\Tecan1\tecan #1 output\" & filename & "*esy")
Else
MsgBox "file " & filename & "not found"
Exit Sub
End If
'open the batch file
''''old iFileNum = FreeFile()
''''old Open fileLocation For Input As #1
''''old Do While Not EOF(iFileNum)
''''old Line Input #iFileNum, stext
Dim fso As New FileSystemObject
Dim fld As Folder
Dim ts As textstream
Set ts = fso.OpenTextFile(fileLocation, ForReading)
While Not ts.AtEndOfStream
stext = ts.ReadLine
letter0 = Mid(stext, 1, 3)
If letter0 <> "A01" And letter0 <> "B01" And letter0 <> "C01" And letter0 <> "D01" And letter0 <> "E01" And letter0 <> "F01" And letter0 <> "G01" And letter0 <> "H01" And letter0 <> "I01" Then
'letter1 = Mid(stext, 7, InStr(8, stext, " ") - 7)
letter1 = Mid(stext, 7, InStr(8, stext, " ") - InStr(1, stext, " ") - 3)
Windows("Batch_XXXX revised.xlsm").Activate
Call ProcessVialPosition(letter0, i)
Cells(i, 3) = letter1
i = i + 1
End If
Wend
ts.Close
''''old Loop
''''old Close #1
Cells(2, 2) = filename
Cells(1, 2) = p
Cells(1, 4) = p1
save_template ("\\Centos5\ls-data\Interface\TF1\THC worklists\" & filename & "_THC" & ".txt")
End Sub
and for some reason it exists out of it at seemingly random points
how do i catch where it exists this sub and how do i catch the error?

Answer 1

You need some error handling code!
Sub open_esy(filename, p As String, p1 As Integer)
On Error Goto Err_open_esy
... your sub here ...
Exit_open_esy:
Exit Sub
Err_open_esy:
... your error handling code here ...
... you can grab line numbers too if you insert them above ...
MyUniversalErrorHandler(Err.Number, Err.Description, Erl)
'Erl is the error line number from the above sub/function
End Sub

Answer 2

Are you asking how to track an error that seemingly is not being raised? If so to disable all error handling in the IDE click Tools->Options->General->Break on all Errors
Failing that you will need to set a breakpoint and step throught the code.